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Detailed Assemblies for an Airtight Small Home

173 points by georgeoliver 5y ago

nvahalik 5y ago
How well do these operate if the electricity fails? If it’s airtight wouldn’t you eventually run out of oxygen?
- wffurr 5y ago
  You can open the door or window.
  - senectus1 5y ago
    assuming you wake up in time :-P
  - carimura 5y ago
    perri-air cans
    - zhengyi13 4y ago
      ... I don't suppose the code on your luggage is 1 - 2 - 3 - 4 - 5?
  - ars 5y ago
    While you are sleeping? But according to google it would take a week to die from too much CO2 in a sealed room.
    - senectus1 5y ago
      thats assuming there isn't something else eating the oxygen or pumping CO2 in.
    - Markoff 5y ago
      just install battery powered CO2 detectors then personally I'm not fan of airtight homes
    - bryanrasmussen 4y ago
      hmm, now I suspect Google may be purchasing carbon offsets and piping the extra C02 into people's houses.
    - adrianN 4y ago
      Humans have relatively reliable CO2 detectors built in that wake you up before you die.
- micromacrofoot 4y ago
  A single person in an air-tight average sized room could survive on the available oxygen for about a week. So I suppose if you're in a perfectly air-tight room and no one comes and goes at all or opens a window, you could die eventually. Even if you're relatively reclusive, assuming you go outside once a day to get the mail... you'll be fine.
erwincoumans 5y ago
Breathtaking.
insaneirish 5y ago
As a side note, Fine Homebuilding and its associated property Green Building Advisor (https://www.greenbuildingadvisor.com https://www.greenbuildingadvisor.com) are exceptional sources of information on quality residential construction. HGTV and similarly oriented renovation programming dominate this media, but there is a large community of people trying to do things correctly and making use of the appropriate technology to do so.
- bkjelden 4y ago
  Similarly, their parent company, Taunton Press, publishes a number of DIY-er focused home improvement books. I own a few of them, and I have found every single one to be a worthwhile purchase.
VectorLock 5y ago
How much does this construction cost vs. standard building? Looks like it could be relatively cost competitive.
- anon23anon 5y ago
  there's another article on that site where she talks about price - it costs her 320k but keep in mind that didn't include the land, her blue prints or all the sweat equity she point in.
  - rubidium 4y ago
    Just over 2x standard price it seems given the materials and labor.
- insaneirish 5y ago
  If you are a builder that executes these details on every project, the cost impact is manageable. When you consider that houses are largely financed and also have operating costs that are dependent on energy efficiency, better built homes make sense on a cash flow basis. However, the real estate industry does not properly value energy efficient projects, and most builders don't execute these details often, so they end up costing more than they should. Another article from Fine Homebuilding goes over some of these issues: https://www.finehomebuilding.com/project-guides/insulation/dont-build-better-houses https://www.finehomebuilding.com/project-guides/insulation/d...
- kkfx 4y ago
  Here (France, and my original country, Italy) costs are complicated to judge: in mere raw materials the cost is far lower for new wood frame houses, but in term of final price is significantly higher, partially because they are a relatively new concept in south/central EU and partially because most enterprise are small ones who do not work much in "modern" terms than in their own workers experience and so they need external enterprises to design and test stuff like windows design for passive heating from the Sun, how much cover windows for avoid Sun when climate is hot, how to design low-inertia heating with heat pumps, Canadian well, dimension a solar p.v./aerovoltaic/* systems etc and while those systems are technologically simple they are sold at higher prices for what they are for similar reasons. The lack of mean awareness and expectations probably permit high prices. In cost terms what I can say is essentially: more initial capex, far reduced opex IF anything is well done. Seen inflation capex/opex ratio means reduced TCO if you buy to stay for years and years at least, resale value so far is a bit crazy for the already described reasons...
jweir 5y ago
Air tight homes and health problems. https://www.cibsejournal.com/news/airtight-new-homes-creating-serious-health-problems/ https://www.cibsejournal.com/news/airtight-new-homes-creatin...
- ocdtrekkie 5y ago
  It probably would make sense to have controlled and well-managed ventilation in airtight houses. It'd still be more energy efficient to heat and cool at a particular ventilation point rather than have what traditional houses have... a lot of leakage everywhere.
  - Johnythree 5y ago
    "makes more sense"? In Europe it's required by law.
- lbotos 5y ago
  FTA: > It was to determine how well the HRVs How many of those homes tested installed a proper mechanical ventilation system? Anyone that is serious about air tightness will tell you that you need to manage the air transfer with an HRV or an ERV so it's filtered, controlled, and avoids these problems. --- I found the study you are quoting: https://pureadmin.qub.ac.uk/ws/portalfiles/portal/31281945/Cse_study.pdf https://pureadmin.qub.ac.uk/ws/portalfiles/portal/31281945/C... Results from the occupant interviews suggest inadequate knowledge of the ventilation system, with all Code 4 homes stating ‘not sure’ when asked about various features of the MVHR system, including the current settings, changing of filters, boost mode function and location of controls. Knowledge of the MVHR system was considerably lacking in Code 4 homes. All households stated that they did not know where the controls for the system were located, or how to change the settings. They asked people who moved into "airtight" social housing if they understood how the systems worked to keep the air moving and people said no. No wonder they had worse air quality...
  - HPsquared 4y ago
    It's a risk when building homes for the general public, things like ventilation need to be idiot-proof. Maybe a big red warning if the system isn't working properly? Mandatory inspections?
matthewaveryusa 5y ago
I understand that the construction materials were chosen to be healthier, but wouldn’t it be even better to have a ‘loose’ house with those same materials?
- ebrewste 5y ago
  You want to control your ventilation. Making a loose house just means you get ventilation, but not on your terms. HRV/ervs in a tight house allows you to ventilate your house, how you want, where you want. A loose house might be ventilating your house through insulation filled with dust and rat poop. You will never know.
  - mypalmike 5y ago
    In an old house, you will know about the rat poop by the smell after you turn on that new AC unit.
  - aidenn0 5y ago
    I can see daylight between my ceiling and exterior walls, so I know where the air cubes from in my house...
- wyago 5y ago
  In theory if you get just the right number of air exchangers such that the same amount of air moves through as it would with a 'loose' house, you get the same airflow with almost none of the convective heat loss/gain. This is however, very much in theory, since as far as I can tell we're still in the early stages of figuring out how to do airtight houses well. My home was built in ~2006 and has an unhealthy CO2 build-up if I close the windows, since it has no active ventilation whatsoever.
hedora 5y ago
We did something similar recently. This looks like standard, low cost modern construction to me. If you’re in a warmish climate (like the SF bay area), you probably don’t want to insulate the concrete slab. You get lots of passive heating of the slab in winter already, and having the ground suck that heat out is a win almost year round. South facing windows can be designed with an eave, etc to lower passive heating in the summer and increase it in the winter. There are reference maps for this, and an architect can work out the passive heating projections for you. We opted for different insulation (there are new eco friendly spray foams, and rockwool is nice for moisture resistance, etc). We didn’t do the split stud double frame thing, but we’re not in Wisconsin, and the R value for the house is already overkill (with an insulation budget that was a tiny fraction of the cost of the house).
- bombcar 5y ago
  Insulating the slab doesn't matter as much as it may appear, as the ground "below" the house eventually reaches equilibrium. Insulating the side foundation walls can be much more useful. http://www.sensiblehouse.org/nrg_heatloss.htm http://www.sensiblehouse.org/nrg_heatloss.htm
  - kitd 4y ago
    Yes. Here in the UK there's a program called Grand Designs about people building beautiful or innovative bespoke homes. One such was an engineer building a home with insulated foundation walls as you describe, based on academic research done by his father in the 1970s & 80s. IIRC it took c. 18 months for the floor to reach equilibrium, but once there, virtually no other heating was required, winter or summer (in the UK).
- georgeoliver 5y ago
  I build homes. This isn't standard in the US. I don't know how much cost it added -- probably not a lot. 10-20% I'm guessing. But, it's not low-cost.
  - ehnto 5y ago
m0llusk 5y ago
It seems like this could use some testing. How do we know that this really works even in one home? There should be some sensors and metrics to show how well variations work so that the design can be robustly optimized.
- georgeoliver 5y ago
  Good point, it seems from my perspective the industry is focused on blower-door tests and air exchange, where it's then kind of assumed that "you're done". I don't think there's real incentive at this point for residential building intelligence. We might have to wait for the 2nd (3rd?) wave of smart home tech to make it happen.
  - frosted-flakes 4y ago
    Fine Homebuilding ran several articles about installing long-term sensors inside walls in various places around a house that could potentially be troublesome. This was a year or so ago. These sensors (humidity, moisture, temperature, etc.) continuously reported their measurements to some sort of service the homeowner and builder could keep an eye on for any irregularities. The sensors were pretty low cost, if I recall; a few hundred dollars altogether. But its definitely not a common practice.
__d 5y ago
I'm curious about the "vent chute": the asphalt-coated fiberboard above the ceiling insulation, but set below the roof sheathing. It creates a cavity beneath the roof that is vented through the eaves. Anyone know why this is done?
- georgeoliver 5y ago
  Venting the roof is standard in new construction, to protect the roof structure from moisture and excessive heat. They did the fiberboard chute so they could densely pack blown-in cellulose. Otherwise the insulation wouldn't have a good surface to push against (you don't want the insulation to touch the roof sheathing). On typical homes with blown-in ceiling insulation the insulators will staple cardboard against the lower few feet of roof framing, creating a similar vent space from eave to ridge. This home's ceiling R-value of 82 is about 2.5 times standard.
  - __d 4y ago
    Thanks for the details. Do you know why this isn't done for walls as well? It seems like the cellulose is packed directly against both the interior and exterior surfaces of the walls. Is it simply that hot air rises, and so it's needed more for the roof?
    - flyingfences 4y ago
      It is done for some walls, but it's much less common. Part of the issue is that, yes, hot air rises, so a lot more moisture will find its way to the roof than to the walls. Part of the issue is that roofs are (traditionally) sealed much more thoroughly than walls (because rain falls on roofs), so the moisture has a harder time getting out. The ventilation channels provide an egress for the moisture below the sealed roof surface. A big part of the issue, at least in many climates, is snowfall. If it's cold outside and warm inside the house, any snow accumulated on the roof is melted from beneath and not from above. As the slush and water try to run down the roof under the unmelted snow, ice dams can form that prevent effective drainage; water pools and leaks down through the roof. A ventilation channel under the roof surface keeps the surface at or near outdoor temperatures, so the heat of the house doesn't melt the snow from beneath.
phkamp 5y ago
That's pretty much how a modern Danish mass-produced house is built, modulus some form language details.
a1371 5y ago
It's interesting to me that hacker news likes building-related content so much, which happens to be my education other than... well, computers. Air tightness is a critical step forward. I'm glad we are talking about it. Thinking more holistically, I would not go with the double-stud wall. You get lots of thermal bridging, and when it gets cold, your outer studs freeze. I know it's considered a straightforward system, but venturing out of one's comfort zone to do an exterior insulated system has enormous durability and performance benefits. Let's build our homes for centuries, not decades, folks!
- willis936 4y ago
  Home ownership is a luxury everyone wants. I can't imagine people don't salivate at the idea of a sturdy, comfortable, private nest. The only class of people who can afford it are people with incomes on par with tech workers.
  - pc86 4y ago
    Patently untrue.
  - bombcar 4y ago
    The national rate of homeownership in the US is 64.8%. That's a hellalotta tech workers.
- tejohnso 4y ago
  > You get lots of thermal bridging The way they did it with those gussets, it seems so. But I don't think double studded walls always imply more thermal bridging than single stud walls where typically every 16 inches there's a complete thermal bridge. I think the double studded wall has proven its effectiveness. > your outer studs freeze Well if they don't freeze, you're heating them. So I would think the outer studs should freeze. > venturing out of one's comfort zone to do an exterior insulated system has enormous durability and performance benefits Any similarly detailed writeups of this?
  - grae_QED 4y ago
WalterBright 5y ago
I bought a CO2 monitor. What a shock it was to see my office go over 1000ppm. I had no idea. Now I crack the window, and tweak that till the CO2 stays below 600 or thereabouts.
- acidburnNSA 5y ago
  I got one too, and a PM2.5 laser sensor. It's a huge challenge during wildfire season to keep the PM2.5 and CO2 both good. Needs filtered HVAC to actually do it. I prefer high CO₂ over high PM2.5 of course.
- ramraj07 4y ago
  Aren’t there heat exchanging ventillation systems that do this (maybe even better) without wasting a ton of energy?
  - gambiting 4y ago
    Opening a window is free, and not everyone has the freedom to modify their living arrangements(rented houses etc)
    - lultimouomo 4y ago
      Opening a window in winter in Wisconsin is very much not free... It's a classic OPEX vs. CAPEX tradeoff, plus the climate impact (of course building the ventilation system has a climate impact too, so there is a tradeoff there as well).
      - dwighttk 4y ago
        The one winter I lived in MN I had to open my windows or else the central heating in my apartment would have baked me alive.
        mattkrause 4y ago
        In a weird full-circle sort of way, that was (sometimes) the point: it was to allow fresh air to circulate even on very cold days—-and during a pandemic, even. https://www.bloomberg.com/news/articles/2020-08-05/the-curious-history-of-steam-heat-and-pandemics https://www.bloomberg.com/news/articles/2020-08-05/the-curio...
basicplus2 5y ago
Pest Control companies will not give Termite treatment because they cannot give guarantee with the xps foam giving a direct pathway for termites into wall framework
Markoff 5y ago
Why would you want airtight home (unless you are WW3 prepper)? Sounds to me like asking for problems with mold and stale air. But I guess I should not be surprised seeing supposedly intelligent people wearing face masks for health reasons.
- koonsolo 4y ago
  You need a ventilation system that recoups the heat of your house. That means you have air inflow in dry rooms, and air outflow in wet rooms. The cold outside air going in gets heated up by the warm inside air going out. Very efficient way of keeping your house warm. That's why it's used a lot in northern European countries.
- deleted 4y ago
  [deleted]
- InCityDreams 4y ago
  >...seeing supposedly intelligent people wearing face masks for health reasons. Are you including doctors, nurses, vets etc during surgery?
  - Markoff 4y ago
    Obviously not.
londons_explore 4y ago
The main reason to make a building airtight is for energy efficiency. But it's pointless to go to such lengths for airtightness if you have massive thermal bridges in the walls and roof in so many places. If you want to be really efficient, the insulation should be constant thickness with no nails or screws poking into it, and certainly no bits of wood across it. Since the insulation has no mechanical strength, that really means you're building two houses - an inner house and an outer house, both of which need to stand up without the help of the other.
- rapjr9 4y ago
  Building a house within a house would also add a lot of soundproofing. I wonder if anyone has studied whether people like or dislike not being able to hear what is going on outside the house. Seems like there would be some safety issues, like you can't hear someone outside calling for help and can't hear how intense a storm is or if a car/truck drives up, but on the good side you also can't hear the neighbors lawn mower and wood chipper. Some people may like feeling connected audibly to the outside world and feel more isolated if they can't hear nature while others may like that it makes the outside world go away. It may not be possible to hear wind chimes. An emergency siren may be difficult to hear, though emergency sirens are not used much any more in the USA, except near nuclear power plants and such. Maybe that needs to change with climate change. In fact, changing climate may need to be part of the calculation on how houses are built (not just increased wind resistance but also estimates of how warm/cold the area will be year round in the future.) It would be great if houses could be 3D printed so people are not limited by increased costs due to homebuilders not upgrading their skills. House design may need to change radically on the East Coast (Nor'easters's) and in Tornado Alley and on the South coast (hurricanes).
- frosted-flakes 4y ago
  I disagree. Airtightness is far more important than insulation. Insulation is worthless if air currents can simply carry the heat and bypass the insulation. And unless you're building an ICF house, some minor thermal bridging is unavoidable. But it does not matter because you can just insulate more somewhere else to make up for it. Exterior foamboard insulation around the entirety of the house is already quite common and cost-effective.
kqvamxurcagg 4y ago
Is there a risk of condensation, damp and mould from homes with excessive insulation? Perhaps someone with some experience could comment.
- de_huit 4y ago
  There is extra risk of course. Good ventilation is required through a counter-flow heat-exchange. This typically gives you the problem of too low humidity, as you remove humid air and get condensation in the heat exchange. There is risk of condensation in the walls. The internal warm layer is airtight, but the walls need to be ably to breath to the outside. Your wood can rot if you make mistakes here, especially on small leaks in the airtight layer. So air-tightness actually is needed to prevent too much condensation in the construction. This all supposes that warm is inside and cold outside, as is typical where I live. In reverse conditions, with hot humid weather and cooling inside, condensation is likely in the walls, as the airtight layer is on the cold side of the wall now. So condensation in the construction is unavoidable. I used an online calculator to decide my material use [1] to estimate how often it does happen, and how long it typically takes to dry. Inside my home, I need a humidifier, this winter it was often below 30%. [1] https://www.ubakus.com/ https://www.ubakus.com/
- jeffbee 4y ago
  If you don't analyze it properly there's always the risk of condensation in the walls, but that risk is far higher from uninsulated walls. With uninsulated cavity walls you have room temperature + room humidity on the interior, and a sharp gradient to outside temperature within the wall, where all the moisture condenses in the winter. Worst possible situation. There's tons of published guidelines about moisture in insulated walls. The easiest thing to build without making some fatal mistake is to put the insulation on the exterior, with a ventilated screen between it and the wall cladding. The best solution also depends on your local climate. See e.g. https://www.nrel.gov/docs/fy13osti/56709.pdf https://www.nrel.gov/docs/fy13osti/56709.pdf
divan 4y ago
Is there version of this article without all this bloat? https://imgur.com/KQavz34 https://imgur.com/KQavz34
sidewndr46 4y ago
While always neat to read about, I have no idea how you'd ever build one of these homes where I live. If you look at new construction, the poor quality work usually means the the home doesn't even meet the existing weatherization standards. Not to mention you'd have to convince an inspector that everything done is to code. While I'm always impressed with such structures, they seem mostly out of reach for someone living in suburban america.
- sudden_dystopia 4y ago
  I think this dude built it himself. My father in law and my grandpa both built their own homes that they still live in today, neither one had any professional construction experience. Not nearly to this standard, but nobody cared about this sort of thing back the. And they didn’t have YouTube to solve problems.
- bluGill 4y ago
  > the poor quality work I keep hearing that, but those who are in the trade listen to engineers who have done real analysis. What looks good often is bad, what looks bad is often good.
  - sidewndr46 4y ago
    Are you stating that the guy nailing zip sheathing on the side of a house talks to the engineer who designed it?
    - JKCalhoun 4y ago
      My assumption: that the guy is even nailing ZIP sheathing is doing so because some engineer determined it was an improvement over previous construction techniques. (But maybe it is just cheaper.)
      - Inhibit 4y ago
        It saves on labor. ZIP doesn't require an extra layer for impermeability of the OSB; just seal up the joints with acrylic tape and you're done. Better? No idea. Although there might be less to screw up unless someone cost-saves by not installing the spec tape (it really is necessary).
verisimi 4y ago
You can see photos of the finished house here: https://www.finehomebuilding.com/2022/04/19/high-performance-demonstration-home https://www.finehomebuilding.com/2022/04/19/high-performance... Airtight it may be, but its no thing of beauty - at least not to me. I mean, its ok - but to me it is just channelling the form of a 2 bed flat into a house. I'm feeling claustrophobic just looking at it.. It looks like there are pleasant nature views all around, but all the effort seems to have been towards shielding the occupants from them!
- bombcar 4y ago
  I mean to be honest it looks like a doublewide manufactured home, but cost like a 3400 sq ft. But if it's what you like, go for it I guess.
nerdkid93 4y ago
Matt Risinger is a builder based out of Austin, TX that has a lot of videos detailing how to build high performance, airtight homes. https://youtube.com/c/MattRisinger https://youtube.com/c/MattRisinger

173 points by georgeoliver 5y ago

nvahalik 5y ago

How well do these operate if the electricity fails? If it’s airtight wouldn’t you eventually run out of oxygen?

wffurr 5y ago
You can open the door or window.
- senectus1 5y ago
  assuming you wake up in time :-P
- carimura 5y ago
  perri-air cans
  - zhengyi13 4y ago
    ... I don't suppose the code on your luggage is 1 - 2 - 3 - 4 - 5?
- ars 5y ago
  While you are sleeping? But according to google it would take a week to die from too much CO2 in a sealed room.
  - senectus1 5y ago
    thats assuming there isn't something else eating the oxygen or pumping CO2 in.
  - Markoff 5y ago
    just install battery powered CO2 detectors then personally I'm not fan of airtight homes
  - bryanrasmussen 4y ago
    hmm, now I suspect Google may be purchasing carbon offsets and piping the extra C02 into people's houses.
  - adrianN 4y ago
    Humans have relatively reliable CO2 detectors built in that wake you up before you die.
micromacrofoot 4y ago
A single person in an air-tight average sized room could survive on the available oxygen for about a week. So I suppose if you're in a perfectly air-tight room and no one comes and goes at all or opens a window, you could die eventually. Even if you're relatively reclusive, assuming you go outside once a day to get the mail... you'll be fine.

erwincoumans 5y ago

Breathtaking.

insaneirish 5y ago

As a side note, Fine Homebuilding and its associated property Green Building Advisor (https://www.greenbuildingadvisor.com https://www.greenbuildingadvisor.com) are exceptional sources of information on quality residential construction. HGTV and similarly oriented renovation programming dominate this media, but there is a large community of people trying to do things correctly and making use of the appropriate technology to do so.

bkjelden 4y ago
Similarly, their parent company, Taunton Press, publishes a number of DIY-er focused home improvement books. I own a few of them, and I have found every single one to be a worthwhile purchase.

VectorLock 5y ago

How much does this construction cost vs. standard building? Looks like it could be relatively cost competitive.

anon23anon 5y ago
there's another article on that site where she talks about price - it costs her 320k but keep in mind that didn't include the land, her blue prints or all the sweat equity she point in.
- rubidium 4y ago
  Just over 2x standard price it seems given the materials and labor.
insaneirish 5y ago
If you are a builder that executes these details on every project, the cost impact is manageable. When you consider that houses are largely financed and also have operating costs that are dependent on energy efficiency, better built homes make sense on a cash flow basis. However, the real estate industry does not properly value energy efficient projects, and most builders don't execute these details often, so they end up costing more than they should. Another article from Fine Homebuilding goes over some of these issues: https://www.finehomebuilding.com/project-guides/insulation/dont-build-better-houses https://www.finehomebuilding.com/project-guides/insulation/d...
kkfx 4y ago
Here (France, and my original country, Italy) costs are complicated to judge: in mere raw materials the cost is far lower for new wood frame houses, but in term of final price is significantly higher, partially because they are a relatively new concept in south/central EU and partially because most enterprise are small ones who do not work much in "modern" terms than in their own workers experience and so they need external enterprises to design and test stuff like windows design for passive heating from the Sun, how much cover windows for avoid Sun when climate is hot, how to design low-inertia heating with heat pumps, Canadian well, dimension a solar p.v./aerovoltaic/* systems etc and while those systems are technologically simple they are sold at higher prices for what they are for similar reasons. The lack of mean awareness and expectations probably permit high prices. In cost terms what I can say is essentially: more initial capex, far reduced opex IF anything is well done. Seen inflation capex/opex ratio means reduced TCO if you buy to stay for years and years at least, resale value so far is a bit crazy for the already described reasons...

jweir 5y ago

Air tight homes and health problems. https://www.cibsejournal.com/news/airtight-new-homes-creating-serious-health-problems/ https://www.cibsejournal.com/news/airtight-new-homes-creatin...

ocdtrekkie 5y ago
It probably would make sense to have controlled and well-managed ventilation in airtight houses. It'd still be more energy efficient to heat and cool at a particular ventilation point rather than have what traditional houses have... a lot of leakage everywhere.
- Johnythree 5y ago
  "makes more sense"? In Europe it's required by law.
lbotos 5y ago
FTA: > It was to determine how well the HRVs How many of those homes tested installed a proper mechanical ventilation system? Anyone that is serious about air tightness will tell you that you need to manage the air transfer with an HRV or an ERV so it's filtered, controlled, and avoids these problems. --- I found the study you are quoting: https://pureadmin.qub.ac.uk/ws/portalfiles/portal/31281945/Cse_study.pdf https://pureadmin.qub.ac.uk/ws/portalfiles/portal/31281945/C... Results from the occupant interviews suggest inadequate knowledge of the ventilation system, with all Code 4 homes stating ‘not sure’ when asked about various features of the MVHR system, including the current settings, changing of filters, boost mode function and location of controls. Knowledge of the MVHR system was considerably lacking in Code 4 homes. All households stated that they did not know where the controls for the system were located, or how to change the settings. They asked people who moved into "airtight" social housing if they understood how the systems worked to keep the air moving and people said no. No wonder they had worse air quality...
- HPsquared 4y ago
  It's a risk when building homes for the general public, things like ventilation need to be idiot-proof. Maybe a big red warning if the system isn't working properly? Mandatory inspections?

matthewaveryusa 5y ago

I understand that the construction materials were chosen to be healthier, but wouldn’t it be even better to have a ‘loose’ house with those same materials?

ebrewste 5y ago
You want to control your ventilation. Making a loose house just means you get ventilation, but not on your terms. HRV/ervs in a tight house allows you to ventilate your house, how you want, where you want. A loose house might be ventilating your house through insulation filled with dust and rat poop. You will never know.
- mypalmike 5y ago
  In an old house, you will know about the rat poop by the smell after you turn on that new AC unit.
- aidenn0 5y ago
  I can see daylight between my ceiling and exterior walls, so I know where the air cubes from in my house...
wyago 5y ago
In theory if you get just the right number of air exchangers such that the same amount of air moves through as it would with a 'loose' house, you get the same airflow with almost none of the convective heat loss/gain. This is however, very much in theory, since as far as I can tell we're still in the early stages of figuring out how to do airtight houses well. My home was built in ~2006 and has an unhealthy CO2 build-up if I close the windows, since it has no active ventilation whatsoever.

hedora 5y ago

We did something similar recently. This looks like standard, low cost modern construction to me. If you’re in a warmish climate (like the SF bay area), you probably don’t want to insulate the concrete slab. You get lots of passive heating of the slab in winter already, and having the ground suck that heat out is a win almost year round. South facing windows can be designed with an eave, etc to lower passive heating in the summer and increase it in the winter. There are reference maps for this, and an architect can work out the passive heating projections for you. We opted for different insulation (there are new eco friendly spray foams, and rockwool is nice for moisture resistance, etc). We didn’t do the split stud double frame thing, but we’re not in Wisconsin, and the R value for the house is already overkill (with an insulation budget that was a tiny fraction of the cost of the house).

bombcar 5y ago
Insulating the slab doesn't matter as much as it may appear, as the ground "below" the house eventually reaches equilibrium. Insulating the side foundation walls can be much more useful. http://www.sensiblehouse.org/nrg_heatloss.htm http://www.sensiblehouse.org/nrg_heatloss.htm
- kitd 4y ago
  Yes. Here in the UK there's a program called Grand Designs about people building beautiful or innovative bespoke homes. One such was an engineer building a home with insulated foundation walls as you describe, based on academic research done by his father in the 1970s & 80s. IIRC it took c. 18 months for the floor to reach equilibrium, but once there, virtually no other heating was required, winter or summer (in the UK).
georgeoliver 5y ago
I build homes. This isn't standard in the US. I don't know how much cost it added -- probably not a lot. 10-20% I'm guessing. But, it's not low-cost.
- ehnto 5y ago

m0llusk 5y ago

It seems like this could use some testing. How do we know that this really works even in one home? There should be some sensors and metrics to show how well variations work so that the design can be robustly optimized.

georgeoliver 5y ago
Good point, it seems from my perspective the industry is focused on blower-door tests and air exchange, where it's then kind of assumed that "you're done". I don't think there's real incentive at this point for residential building intelligence. We might have to wait for the 2nd (3rd?) wave of smart home tech to make it happen.
- frosted-flakes 4y ago
  Fine Homebuilding ran several articles about installing long-term sensors inside walls in various places around a house that could potentially be troublesome. This was a year or so ago. These sensors (humidity, moisture, temperature, etc.) continuously reported their measurements to some sort of service the homeowner and builder could keep an eye on for any irregularities. The sensors were pretty low cost, if I recall; a few hundred dollars altogether. But its definitely not a common practice.

__d 5y ago

I'm curious about the "vent chute": the asphalt-coated fiberboard above the ceiling insulation, but set below the roof sheathing. It creates a cavity beneath the roof that is vented through the eaves. Anyone know why this is done?

georgeoliver 5y ago
Venting the roof is standard in new construction, to protect the roof structure from moisture and excessive heat. They did the fiberboard chute so they could densely pack blown-in cellulose. Otherwise the insulation wouldn't have a good surface to push against (you don't want the insulation to touch the roof sheathing). On typical homes with blown-in ceiling insulation the insulators will staple cardboard against the lower few feet of roof framing, creating a similar vent space from eave to ridge. This home's ceiling R-value of 82 is about 2.5 times standard.
- __d 4y ago
  Thanks for the details. Do you know why this isn't done for walls as well? It seems like the cellulose is packed directly against both the interior and exterior surfaces of the walls. Is it simply that hot air rises, and so it's needed more for the roof?
  - flyingfences 4y ago
    It is done for some walls, but it's much less common. Part of the issue is that, yes, hot air rises, so a lot more moisture will find its way to the roof than to the walls. Part of the issue is that roofs are (traditionally) sealed much more thoroughly than walls (because rain falls on roofs), so the moisture has a harder time getting out. The ventilation channels provide an egress for the moisture below the sealed roof surface. A big part of the issue, at least in many climates, is snowfall. If it's cold outside and warm inside the house, any snow accumulated on the roof is melted from beneath and not from above. As the slush and water try to run down the roof under the unmelted snow, ice dams can form that prevent effective drainage; water pools and leaks down through the roof. A ventilation channel under the roof surface keeps the surface at or near outdoor temperatures, so the heat of the house doesn't melt the snow from beneath.

phkamp 5y ago

That's pretty much how a modern Danish mass-produced house is built, modulus some form language details.

a1371 5y ago

It's interesting to me that hacker news likes building-related content so much, which happens to be my education other than... well, computers. Air tightness is a critical step forward. I'm glad we are talking about it. Thinking more holistically, I would not go with the double-stud wall. You get lots of thermal bridging, and when it gets cold, your outer studs freeze. I know it's considered a straightforward system, but venturing out of one's comfort zone to do an exterior insulated system has enormous durability and performance benefits. Let's build our homes for centuries, not decades, folks!

willis936 4y ago
Home ownership is a luxury everyone wants. I can't imagine people don't salivate at the idea of a sturdy, comfortable, private nest. The only class of people who can afford it are people with incomes on par with tech workers.
- pc86 4y ago
  Patently untrue.
- bombcar 4y ago
  The national rate of homeownership in the US is 64.8%. That's a hellalotta tech workers.
tejohnso 4y ago
> You get lots of thermal bridging The way they did it with those gussets, it seems so. But I don't think double studded walls always imply more thermal bridging than single stud walls where typically every 16 inches there's a complete thermal bridge. I think the double studded wall has proven its effectiveness. > your outer studs freeze Well if they don't freeze, you're heating them. So I would think the outer studs should freeze. > venturing out of one's comfort zone to do an exterior insulated system has enormous durability and performance benefits Any similarly detailed writeups of this?
- grae_QED 4y ago

WalterBright 5y ago

I bought a CO2 monitor. What a shock it was to see my office go over 1000ppm. I had no idea. Now I crack the window, and tweak that till the CO2 stays below 600 or thereabouts.

acidburnNSA 5y ago
I got one too, and a PM2.5 laser sensor. It's a huge challenge during wildfire season to keep the PM2.5 and CO2 both good. Needs filtered HVAC to actually do it. I prefer high CO₂ over high PM2.5 of course.
ramraj07 4y ago
Aren’t there heat exchanging ventillation systems that do this (maybe even better) without wasting a ton of energy?
- gambiting 4y ago
  Opening a window is free, and not everyone has the freedom to modify their living arrangements(rented houses etc)
  - lultimouomo 4y ago
    Opening a window in winter in Wisconsin is very much not free... It's a classic OPEX vs. CAPEX tradeoff, plus the climate impact (of course building the ventilation system has a climate impact too, so there is a tradeoff there as well).
    - dwighttk 4y ago
      The one winter I lived in MN I had to open my windows or else the central heating in my apartment would have baked me alive.
      - mattkrause 4y ago
        In a weird full-circle sort of way, that was (sometimes) the point: it was to allow fresh air to circulate even on very cold days—-and during a pandemic, even. https://www.bloomberg.com/news/articles/2020-08-05/the-curious-history-of-steam-heat-and-pandemics https://www.bloomberg.com/news/articles/2020-08-05/the-curio...

basicplus2 5y ago

Pest Control companies will not give Termite treatment because they cannot give guarantee with the xps foam giving a direct pathway for termites into wall framework

Markoff 5y ago

Why would you want airtight home (unless you are WW3 prepper)? Sounds to me like asking for problems with mold and stale air. But I guess I should not be surprised seeing supposedly intelligent people wearing face masks for health reasons.

koonsolo 4y ago
You need a ventilation system that recoups the heat of your house. That means you have air inflow in dry rooms, and air outflow in wet rooms. The cold outside air going in gets heated up by the warm inside air going out. Very efficient way of keeping your house warm. That's why it's used a lot in northern European countries.
deleted 4y ago
[deleted]
InCityDreams 4y ago
>...seeing supposedly intelligent people wearing face masks for health reasons. Are you including doctors, nurses, vets etc during surgery?
- Markoff 4y ago
  Obviously not.

londons_explore 4y ago

The main reason to make a building airtight is for energy efficiency. But it's pointless to go to such lengths for airtightness if you have massive thermal bridges in the walls and roof in so many places. If you want to be really efficient, the insulation should be constant thickness with no nails or screws poking into it, and certainly no bits of wood across it. Since the insulation has no mechanical strength, that really means you're building two houses - an inner house and an outer house, both of which need to stand up without the help of the other.

rapjr9 4y ago
Building a house within a house would also add a lot of soundproofing. I wonder if anyone has studied whether people like or dislike not being able to hear what is going on outside the house. Seems like there would be some safety issues, like you can't hear someone outside calling for help and can't hear how intense a storm is or if a car/truck drives up, but on the good side you also can't hear the neighbors lawn mower and wood chipper. Some people may like feeling connected audibly to the outside world and feel more isolated if they can't hear nature while others may like that it makes the outside world go away. It may not be possible to hear wind chimes. An emergency siren may be difficult to hear, though emergency sirens are not used much any more in the USA, except near nuclear power plants and such. Maybe that needs to change with climate change. In fact, changing climate may need to be part of the calculation on how houses are built (not just increased wind resistance but also estimates of how warm/cold the area will be year round in the future.) It would be great if houses could be 3D printed so people are not limited by increased costs due to homebuilders not upgrading their skills. House design may need to change radically on the East Coast (Nor'easters's) and in Tornado Alley and on the South coast (hurricanes).
frosted-flakes 4y ago
I disagree. Airtightness is far more important than insulation. Insulation is worthless if air currents can simply carry the heat and bypass the insulation. And unless you're building an ICF house, some minor thermal bridging is unavoidable. But it does not matter because you can just insulate more somewhere else to make up for it. Exterior foamboard insulation around the entirety of the house is already quite common and cost-effective.

kqvamxurcagg 4y ago

Is there a risk of condensation, damp and mould from homes with excessive insulation? Perhaps someone with some experience could comment.

de_huit 4y ago
There is extra risk of course. Good ventilation is required through a counter-flow heat-exchange. This typically gives you the problem of too low humidity, as you remove humid air and get condensation in the heat exchange. There is risk of condensation in the walls. The internal warm layer is airtight, but the walls need to be ably to breath to the outside. Your wood can rot if you make mistakes here, especially on small leaks in the airtight layer. So air-tightness actually is needed to prevent too much condensation in the construction. This all supposes that warm is inside and cold outside, as is typical where I live. In reverse conditions, with hot humid weather and cooling inside, condensation is likely in the walls, as the airtight layer is on the cold side of the wall now. So condensation in the construction is unavoidable. I used an online calculator to decide my material use [1] to estimate how often it does happen, and how long it typically takes to dry. Inside my home, I need a humidifier, this winter it was often below 30%. [1] https://www.ubakus.com/ https://www.ubakus.com/
jeffbee 4y ago
If you don't analyze it properly there's always the risk of condensation in the walls, but that risk is far higher from uninsulated walls. With uninsulated cavity walls you have room temperature + room humidity on the interior, and a sharp gradient to outside temperature within the wall, where all the moisture condenses in the winter. Worst possible situation. There's tons of published guidelines about moisture in insulated walls. The easiest thing to build without making some fatal mistake is to put the insulation on the exterior, with a ventilated screen between it and the wall cladding. The best solution also depends on your local climate. See e.g. https://www.nrel.gov/docs/fy13osti/56709.pdf https://www.nrel.gov/docs/fy13osti/56709.pdf

divan 4y ago

Is there version of this article without all this bloat? https://imgur.com/KQavz34 https://imgur.com/KQavz34

sidewndr46 4y ago

While always neat to read about, I have no idea how you'd ever build one of these homes where I live. If you look at new construction, the poor quality work usually means the the home doesn't even meet the existing weatherization standards. Not to mention you'd have to convince an inspector that everything done is to code. While I'm always impressed with such structures, they seem mostly out of reach for someone living in suburban america.

sudden_dystopia 4y ago
I think this dude built it himself. My father in law and my grandpa both built their own homes that they still live in today, neither one had any professional construction experience. Not nearly to this standard, but nobody cared about this sort of thing back the. And they didn’t have YouTube to solve problems.
bluGill 4y ago
> the poor quality work I keep hearing that, but those who are in the trade listen to engineers who have done real analysis. What looks good often is bad, what looks bad is often good.
- sidewndr46 4y ago
  Are you stating that the guy nailing zip sheathing on the side of a house talks to the engineer who designed it?
  - JKCalhoun 4y ago
    My assumption: that the guy is even nailing ZIP sheathing is doing so because some engineer determined it was an improvement over previous construction techniques. (But maybe it is just cheaper.)
    - Inhibit 4y ago
      It saves on labor. ZIP doesn't require an extra layer for impermeability of the OSB; just seal up the joints with acrylic tape and you're done. Better? No idea. Although there might be less to screw up unless someone cost-saves by not installing the spec tape (it really is necessary).

verisimi 4y ago

You can see photos of the finished house here: https://www.finehomebuilding.com/2022/04/19/high-performance-demonstration-home https://www.finehomebuilding.com/2022/04/19/high-performance... Airtight it may be, but its no thing of beauty - at least not to me. I mean, its ok - but to me it is just channelling the form of a 2 bed flat into a house. I'm feeling claustrophobic just looking at it.. It looks like there are pleasant nature views all around, but all the effort seems to have been towards shielding the occupants from them!

bombcar 4y ago
I mean to be honest it looks like a doublewide manufactured home, but cost like a 3400 sq ft. But if it's what you like, go for it I guess.

nerdkid93 4y ago

Matt Risinger is a builder based out of Austin, TX that has a lot of videos detailing how to build high performance, airtight homes. https://youtube.com/c/MattRisinger https://youtube.com/c/MattRisinger