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Ask HN: Best HVAC system for a new house?
I know nothing about building houses. I've never even bought a house. However, we bought some land, got an architect to draft up some custom plans, now we're in the bidding phase.
What sorts of HVAC systems are out there and as a nerd/engineer, should I want a completely analog system or 'state of the art' HVAC system or something in between?
Besides the usual, I'd like as much fine grained control over different parts of the house, at the very least control separately the temperatures in the basement, 1st and 2nd floor.
- vyrotek 6y agoYou'll get a better response posting this to an HVAC specific Reddit.
- m463 6y agobut it's nice for us who spend our time here and have given up reddit.
- jxramos 6y agoI'm not sure entirely, but there's a ton of products over here worth poring over https://www.supplyhouse.com/ https://www.supplyhouse.com/
- ip26 6y agoTake a look at air source heat pumps, e.g. Mitsubishi. They are (probably) the future of HVAC. They also make it pretty easy to do a zoned system, e.g. separate control for different parts of the house.
- hellonoko 6y agoThis wasn't something your architect discussed with you? They should have, this should be an integral part of how your home is designed and functions. Best in what way? Efficiency? Comfort? Initial Cost? Maintenance? Air quality? If you would like a list of resources to dive into this let me know!
- bleepblorp 6y agoLook at the multi-zone minisplit heat pumps from Mitsubishi and Daikin. These systems support room-by-room zoning. They'll do air conditioning in any climate and can be designed to provide heat in conditions down to 5 to 10 degrees below freezing. If you're in a climate that gets colder than that, get either baseboard heaters, or a zoned boiler system, for backup heat for when the heat pumps can't keep up during cold weather. Which option makes the most sense will depend on how cold it gets and for how long.
- ebrewste 6y agoAnd also, hopefully your hvac system will last long enough that you will benefit from your efficient mini splits that 1) are efficient because you didn’t buy the cheapest one, saving you money from an increasing cost electrical rate or expensive PV system and 2) will benefit from a greening electrical system as coal and other dirtier power tech goes away
- mdorazio 6y agoCan confirm this advice - my brother does high-end HVAC install and repair work and I've spent several months with him doing the same over the last two years. Mitsubishi and Daikin are about as good as you can get for high-efficiency minisplits and are a lot less likely to fail on you in a few years than the cheaper brands. Also a quick note on heating in colder climates - take note of what's available in your local area. Electric heating may not be the most cost effective (or most reliable) option in winter.
- ikiris 6y agoDiakin has possibly the shittiest knock off of ecobee firmware Ive ever seen. Enough to nope out of it if i see it in the next apartment. Its infuriating coming from being on a nest prior.
- kelchm 6y agoIf you're talking about the 'ENVi' thermostat [1], it was actually manufactured by ecobee from what I understand. I know Daikin has Honestly, all of the controls for residential mini split systems are pretty awful. My Mitsubishi system has the MHK1 thermostat [2] which is Mitsubishi specific version of the traditional Honeywell thermostat. The newer MHK2 looks a bit more modern, but honestly isn't really any different in function. 1: http://www.daikinac.com/content/residential/residential-controllers/envi-thermostats-and-controls/ http://www.daikinac.com/content/residential/residential-cont... 2: http://www.nonul.mylinkdrive.com/item/MHK1.html http://www.nonul.mylinkdrive.com/item/MHK1.html
- ogre_codes 6y agoThis is a complicated question because the answer relies heavily on where your house is. Living in the Pacific Northwest I'm able to get by with no AC but need decent heat. When I lived in California, air conditioning was kind of a must but heat was pretty much an afterthought. Ideally, engineer your house so you don't need a powerful HVAC system to be comfortable. We have (amazing) insulation so we don't need any air conditioning, but it gets a bit chilly so we are working on installing radiant heat in the floor.
- lotsofpulp 6y agoLiving without AC will be very uncomfortable in the PNW in a 2 story house going forward. It already has been for a few years.
- ogre_codes 6y agoBuild right and you are fine. I'm smack in the middle of the Willamette Valley and our house peaks at a comfortable 72-75 degrees during the hot part of the afternoon. No AC.
- EricE 6y agoIf you routinely have low humidity it's amazing what a whole house fan will let you get away with. It pulls air from the outside in through your house, then exhausts it into the attic. Even on very hot days, as long as the humidity isn't crazy it is very effective at keeping you cool. I routinely go without running AC into days that go into the low 80's. Living in the mid Atlantic I've been pleased about just how much I have been able to use a whole house fan. They have come a long way too. I have one from QuiteCool Systems - instead of a fan bolted directly to the attic rafters with crappy metal louvers that rattle and don't block out drafts when not in operation, it has a powerful fan on a segment of ductwork - when you install you install it so there is a 90 degree bend in the ductwork and it attenuates the vast majority of fan noise. Indeed, I hear more from the motor rumble through the rafters in the attic where it's mounted than I do from the fan/air noise. It comes with an insulated and highly efficient damper too. The system took less than an hour to install and I was easily able to pull power from an outlet in my hall, put in a switch then continue to the attic with the fan. https://quietcoolsystems.com/ https://quietcoolsystems.com/ Mine has more than paid for itself - less than 650 watts vs over 2800 watts if both my AC units are running. The only problem I have is my house is a little over 2800 square feet and if I let it get warm (say I am not home and close the house up then come home hours later) the single fan I have is not powerful enough to cool - I need to add a second unit so I have better peak air flow. I think I will add the unit that has two smaller fans, then at night when I still would like a little airflow but not a hurricane I can have more a gentle breeze. Needing to have more control over airflow at night is something I didn't anticipate. I have tied my home automation system in - I can read the temperature from my Nest thermostats and turn the fan on/off as needed. I also have the scripts check the status of windows/doors through my alarm system. One danger is if you have gas appliances that are not direct vented you can back draft them - my water heater is in my basement and it's not direct vented - it relies on a flue so you need to be careful you don't reverse the flow in the flue. I have a couple of extra CO2 monitors in the basement and after five years have never seen a blip but it is something to be aware of with any gas appliance. Heck if your house isn't balanced a bathroom fan can cause a backdraft in a flue.
- ag56 6y agoDepends so much on your climate. Heat: the best by far is under floor heating (hot water not electric). Each room will have its own thermostat. There will be no cold spots, it will just feel cozy. No air is being cycled around the room keeping dust down. Ventilation: indoor pollution is usually many multiples of outdoor. You want a an MVHR (or MEV) system to exchange the air in the house for fresh air with low heat (energy) loss. AC: You need to move cold air around for this unfortunately. Pumping chilled water through your under floor heating pipes risks condensation in crawl spaces, and even if it doesn’t it simply doesn’t work very well. (Source: I had ‘radiant cooling’ ceiling panels in my last house.) I would look into a mini-duct or ductless AC system so you can control each room individually. In climates that require heat and cooling, it is far more cost effective to go with a standard HVAC system, unfortunately, as you’ll be putting ducts throughout the house for AC. (Why put a separate system in for heating when you could just move hot air around?) But if you want the best, not cheapest, solution you really want under floor heating.
- ubertoop 6y ago> Ventilation: indoor pollution is usually many multiples of outdoor. You want a an MVHR (or MEV) system to exchange the air in the house for fresh air with low heat (energy) loss. Can you expand on this? What is polluting the indoors? How can I verify it's true at my home?
- danielheath 6y agoYour body constantly sheds skin flakes (dust). Tiny mites find those flakes, cover them in enzymes that break down skin, then wait for them to break down enough to eat. When a puff of air lifts the dust into your lungs, those digestive enzymes attack your lungs. Your body produces extra mucus in response, to trap dust on the way in, and inflames the tissue surrounding any damage to prevent infection taking hold. Neither response is pleasant.
- EricE 6y agoAnd if you think that's bad, just do an air sample after running a vacuum. Micron filters or not. It's one of the many reasons I love my central vacuum system - it exhausts outside my home :)
- realitysballs 6y agoI work for a high-end custom residential GC and have see a lot of high end HVAC systems. The new trends are as follows: HRV (heat recovery ventilators) are pretty in. Basically they are auxiliary units that source outside fresh air or exhaust stale air when there is a heat differential between a specific heating/cooling zone and the outside temps. So if you are in a basement that is cold and the outside is hot it will just bring in outside air instead of turning on the heater. Radiant floor heating and radiant cooling zones are also in. And run water through Your floors to heat or cool zones. It is one of the most efficient ways to heat a structure and feels good as well. Geothermal is also pretty in for high-end residences but there is a high first cost to evaluate geothermal potential. Most of these new technologies are usually coupled with standard split-systems or VRF systems and add additional efficiency (life cycle cost value) over the span of occupancy but have higher first costs . Lastly— always consider passive heating and cooling strategies they are highest value options (insulation , shading, glazing specs , solar orientation , landscaping , etc.)
- nullc 6y ago> So if you are in a basement that is cold and the outside is hot it will just bring in outside air instead of turning on the heater. Uh. Purpose of the HRV is to attempt to preserve the inside heat (usually both latent and sensible, using a rotating exchanger wheel) while bringing in fresh outside air. They allow you to seal the building up really good, which is good for energy efficiency, without having insufficient ventilation and getting high CO2 levels. Because they're not perfectly efficient, you can use them to move the inside temp closer to outside-- but just plain outside air exchange would do it better. :)
- sh1mmer 6y agoCurious where you are located. I was talking with our high end GC in Texas and they basically said Geothermal for heat exchange never seems to pan out for clients after the numbers are run. This seemed surprising to me. Some of the other stuff you mentioned came up, we also talked about if homogeneous household temperature was something we cared about because keeping the whole house 68 is way more intensive than having some variance in different spots of the house. Also breezeways are awesome in hot climates.
- zachrose 6y agoI'm not an expert but I am interested in the wisdom of regional and historical architecture for this sort of thing. Look at the old buildings where you are. How did they do it? (You might get less out of this if you're in a place that boomed with air conditioning, but still there are lessons to learn from the indigenous architecture[1] of your region.) [1] https://www.amazon.com/Native-American-Architecture-Peter-Nabokov/dp/0195066650 https://www.amazon.com/Native-American-Architecture-Peter-Na...
- etrautmann 6y agolook into heat pumps! they're basically magic :)
- deleted 6y ago[deleted]
- silexia 6y agoIf you are building a house, I highly recommend watching Essential Craftsman on YouTube. He has a wonderful playlist series on building a spec house that will help you understand what's going on. I even signed up for his Patreon (my first time using that tool).
- FunnyLookinHat 6y agoEssential Craftsman is my favorite YouTube channel! I've been loving the spec-house series.
- ww520 6y agoWhere are you located and what's the usual temperature pattern throughout the year?
- fizixer 6y agoPlan your circulation: in every room, one high vent, one low vent, both with smart open/close, Winter: warm air comes in from the bottom vent, goes out from the top vent Summer: cool air comes in from the top vent, goes out from the bottom vent This dual inlet/outlet role from the same vent will have to be managed by some kind of valves/directer-plates inside the ducts. a smart thermostat in every room Vent open/close percentage controlled by each room's temperature (essentially vent acts like a per-room thermostat, while the main thermostat controls the overall/average temperature). Disclaimer: I'm not an HVAC person.
- t-writescode 6y agoWhy would cool air come in front the top vent in the summer?
- fizixer 6y agoBecause hot air rises. If cool air came in from the bottom vent, all the cool air will accumulate in the bottom half of the room, hot air accumulates in the top half. When you stand up, your face feels hot, feet are cold.
- t-writescode 6y agoRight. So are you meaning more than a vent but also cooling, then? Because it’ll just be hot air up there instead.
- deleted 6y ago[deleted]
- georgeburdell 6y agoI got a Mitsubishi variable speed heat pump installed recently to replace my gas furnace (didn't have AC before). It's extremely quiet, inside and out. I do not recommend it for areas that go well below freezing, though. I want to say the unit is rated down to 20F I believe it comes in mini-split varieties but I did not choose that option as it was more expensive and I didn't like the aesthetics.
- ip26 6y agoFWIW Mitsubishi has a "hyperheat" line of heat pumps meant for climates that do go down below freezing - rated down to -15F or so.
- georgeoliver 6y agoI would strongly encourage you to think less about systems and more about performance goals. * How much energy use? * How much carbon do you want to burn? * How much money do you want to spend year over year? * What kind of indoor air quality do you want to achieve? * What is your comfort zone temperature wise? Then design your system around that. This also encourages thinking about how these goals interact with site conditions: glazing, solar orientation, climate, etc. I don't know the scope of your project but consider getting a mechanical plan drawn up. Most residential projects don't have them and in my opinion (I've been building since 1999) it's a lost opportunity for a better, more efficient installation.
- erikerikson 6y agoHeat pumps and an ERV. Both fairly simple but provide hear/cooling and clean fresh air, respectively and both do so efficiently. There really needs to be an advance but that hasn't happened yet and every knowledgeable HVAC person I spoke with said the "advanced" combination units broke down too much and were overly expensive to acquire, fix, and maintain. Make sure your home is air right with spray foam or something like it.
- oakwhiz 6y agoDon't use spray foam, if not properly mixed and applied there is a risk of the foam off-gassing, continuously producing toxic fumes over a period of months to years, and consisting of chemicals such as isocyanates. The cost of removing the foam once installed is tremendous.
- eyeareque 6y agoSomething with dual zone control, and a nest thermostat for each area. Maybe two systems? Something you should also do is make sure the place has really good insulation and windows/doors. Or you can spend a lot more money and do what the top comment says.
- cottsak 6y agoThe new Tesla one :p
- stunt 6y agoEither the one that the company where I work builds, because I'm building their APIs. Or any other system that is powered by Rust and is fully distributed on AWS must be a good choice. Otherwise, I can also recommend the one that I use in my house because I had no issues with it so far. Now that was a lame joke. But seriously you can find better answers in Reddit or other specialized communities.
- vellum 6y agoDavid Heinemeier Hansson gave a great talk on air quality and touched upon various HVAC systems. One thing that really stuck out, was his claim that you need 80 CFM per person per room. https://www.youtube.com/watch?v=MRqh8oLY7Ik https://www.youtube.com/watch?v=MRqh8oLY7Ik
- donavanm 6y agoDepends on where you live and what your energy costs and options are. Be prepared to pay $$$ as you start adding zones, especially at a “per room” level. In the PNW my todo wishlist is heat pump + zoned underfloor radiant + on demand gas boiler for supplementary heat and household water supply. TBD on cooling via ceiling/floor loops or separate wall mounted chiller/evaporator units. I had gas fired boiler + radiant heat + supplementary resistive heating in each bedroom. I’m currently living with 3 zoned mini splits. Honestly happy enough with both, but structural radiant heat is just the best for comfort.
- galfarragem 6y agoIt's impossible to give an accurate advice without knowing your precise location and climate. As a rule of thumb, as an Architect (the real one), I would start by using the best insulation you can afford. In a good percentage of inhabited places this will guarantee you a livable if not a confortable home. Then, according to your climate and economic environment (wood and derivates, gas, fuel, coal and electricity prices are highly variable depending of your specific location) invest in an heating source.
- EricE 6y agoThe most comfortable I've been in winter is with buildings that have in-floor radiant heat. It would almost be worth living in an area with severe winter as they are a that nice. If the area you are in gets cold, it would be 1st priority for me. I'll be remodeling my bathroom and I will be adding electric heat under the tile - set it to come on a few hours before I get up in the morning - heaven! For cooling, multi-zone mini-splits are hard to beat. Per room control. Most of them are variable speed so they are exceptional at dehumidification in the summer. The heat pump capabilities on them are also tend to be significantly better than traditional HVAC systems. I've added them on to a few rooms and my garage; if I ever build another home or have to do a significant remodel/replacement of an HVAC system I will go with mini-splits. Also no ductwork in unconditioned spaces. If you do go with traditional HVAC and are going to have ductwork in traditionally unconditioned spaces like an attic, look at the recent trends in treating traditionally unconditioned spaces like attics/crawl spaces as condition spaces - there have been a lot of advances in insulation, ventilation, etc. Finally as many others mentioned, if you are building a new home it should be a tight home (tight from air infiltration/leakage) so a heat recovery ventilator is a must. An excellent YouTuber to peruse for lots of great ideas on how to improve on home building is Matt Risigner - I think he goes by The Build Show. There are lots of TV shows and people on YouTube pimping building advice but he's pretty approachable to even those not familiar with construction at all, and I haven't seen him hand out what I would consider off the wall or crazy advice - but he still will push the bounds of what is considered best practices in the industry. Upgrading the right materials for your home can have a HUGE impact. A couple years back there was that major hurricane in Florida and there was the house that the homeowner spent about 20% more on and his survived, and all this neighbors for blocks were literally flattened. Even if you don't have major storms to worry about, well built homes are significantly more comfortable, healthier (I recently had a mold issue due to inadequate ventilation), and could even save you money on heating/cooling.
- EricE 6y agoAnd while not directly HVAC, a comment elsewhere in the thread made me think of another point as far as indoor air quality - consider a central vacuum system. The noisy power unit with the blower can be in a garage or basement (instead of at your feet!), the hose and power head are light. If you don't have carpet and only hardwood/tile/solid surfaces then you can get a hose without electrical for the power head, and a brush wand head - extremely light! My hallways, kitchen and a few high traffic rooms are all solid surfaces and it takes me five minutes to get the hose out, plug it in, vacuum the floor and then put the hose back. Faster than sweeping or mopping and I have a flexible hose that expands/contracts as needed. Very convenient. And best of all (especially since I have allergies) it exhausts all the vacuumed air outside. Central vacuums are far more powerful than any hand operated vacuum you can get - and like a said a heck of a lot quieter too.
- obeone 6y agoThere are 2 aspects to home comfort: Having the right amount of heat in your house, and keeping the temperature in your home from fluctuating. As others have pointed out on this thread, there are many ways to add and remove heat from your home. I would suggest that the second point, the thermal mass of your home, is an often overlooked item that is very easy to design in pre-construction, but very hard to add as an afterthought. Interior stone, concrete, and water (like a fountain, for example) efficiently and perpetually absorb and radiate the existing heat into an already conditioned space in a way that is eminently comfortable.
- EricE 6y agoTimely video on a radiant system with hardwood: https://www.youtube.com/watch?v=qWvoYMf5iC4 https://www.youtube.com/watch?v=qWvoYMf5iC4 If I was going to retire in my house I might just consider something like that!
- hotclimate42 6y agoI guess you don't live very close to the equator? [rant warning] I don't know why, but I'd say at least 70% of the advice I see on The Internet about climate control is advocating for some kind of best-of-class heating solution. The cold-climate-centric mentality is almost as bad as the quite prevalent US-centric mentality one often runs into. Look people, some of us live in a climate where 60F/15C in the day is a miracle & 40F/5C at night is fscking cold! Something like radiant heat flooring would be the biggest waste of money around here. Not even the I-don't-even-know-what-to-do-with-my-money rich people use that shit in their ginormous mansions. The C in HVAC stands for Cooling. And IME cooling is a much harder problem to solve than Heating (so many ways to get heat -- burn shit, run electricity through it, steal some from the ground or sun, etc. But cooling, not as many options, and typically more complicated than heating. /rant
- stevep98 6y agoCheck out Matt Risinger's Youtube channel. He's a builder, but much of his content focuses on lowering the cost of HVAC by making sure your insulation is effective, and your building envelope is draft-free. He does cover equipment too, such as multi-zone systems.
- souprock 6y agoThat stuff is minor. For about $10,000 you can change it out, and you certainly will over the years. Budget about $1000 per year for a normal system, with replacement every 10 years. The serious concern is ductwork. Replacement means ripping open walls, unless you go for the weird industrial look. Fixing your walls is not cheap. Normal ductwork grows a thick layer of toxic black mold. Normal ductwork is impossible to scrub clean. Good ductwork has a hard and perfectly smooth inner surface. It can withstand vigorous scrubbing. It is made of bare uncoated metal that is corrosion-resistant and mold-suppressing. Nickel and copper are great.