4 ms·

Our 50 year old CA house is typical---wood framed with a vented crawl space, so no slab and minimal link to the ground mass. It has only 1970s fiberglass insula

Our 50 year old CA house is typical---wood framed with a vented crawl space, so no slab and minimal link to the ground mass. It has only 1970s fiberglass insulation in the 2x4 framed walls and ceiling, with none beneath the floors. It also has 1970s single pane glass and many southwest-facing windows. We make effective use of the house's thermal inertia in both summer and winter. We lack central air-conditioning and have an inefficient 1970s gas furnace. I can definitely feel the radiant temperature of the house and its content around me. This is linked to the thermal mass and contributes to comfort along with actual air temperature. Our biggest improvements have been modern roofing and DIY heat-rejecting window films. Both seem to reduce the radiant connection between the outdoors and interior, helping in both summer and winter. In summer, nighttime ventilation and daytime closure means our indoor temperature can start low and lag behind the outdoor heat by many hours. At some point in the evening, the falling outdoor temperature meets that indoor and we start ventilating again. During multi-day heat waves, we will see that the house retains heat, increasing both morning lows and evening highs. But, it still lags behind the outdoors and smooths out the peak. In winter, we heat to a more comfortable target for a few hours in early morning and after dusk. We let it coast with a lower baseline target otherwise. During clear days, we get enough solar gain to either hold it steady or even warm the house above our desired set point. Then, the evening heat cycle either holds or brings it back up as the light fades and the walls start to feel a lack of radiant warmth. By the time the house is feeling chilled, we're snug in our bedding and it coasts lower until the next dawn cycle.

wolverine876 3y ago
> modern roofing and DIY heat-rejecting window films What do you use? > nighttime ventilation and daytime closure I do that, it works very well (though depending on the house, of course), but I'm surprised I don't see it as standard advice for homeowners. Even better, an input at a cool spot (near shady grass, etc.), and output with an exhaust fan at the top; auto open/close based on thermostats outside and inside. > In winter, we heat to a more comfortable target for a few hours in early morning and after dusk. Is the early morning heat for efficiency somehow (or just it's too chilly when you wake up after an unheated night). - Also: Our perception is of it being colder when it's colder outside, despite the thermostat being set to the same temperature - that is, we need to set the thermostat a bit higher to not feel chilled. I wonder if our perception of temperature depends on something like the coldest (micro-)draft more than the ambient average.
- saltcured 3y ago
  It saves energy to let the house get colder overnight when we can rely on bedding to keep us warm. With a lower differential between indoors and outdoors, there is less total energy lost to the outside than if we held a constant target. I'm only dropping the set point about 5 degrees, not disabling heat entirely. Then the morning heat is to make it easier to get out of bed and start the day. We stop it again to take advantage of the common solar gain. But also, it doesn't take as much heat to feel comfortable once we've eaten and gotten more active for the day. For the roof, it is just one of the "cool roof" compliant asphalt shingle systems, with full plywood sheathing. We did not retrofit radiant-barrier sheathing, as there is fine print that this could overheat the shingles. As far as I can tell, the same performance to reject solar load in summer also reduces radiant loss in winter. Vaulted ceilings feel less exposed on a cold winter night. For windows, I applied Gila "heat control" film found at the local Home Depot. It is a modestly cool gray tint that looks only a little bit mirror-like from the outside, not too different from modern low-e glass. It takes a little practice to get satisfying results with the DIY application. I just used a spray bottle filled with tap water with a few drops of dishwashing soap, rather than any proprietary application fluid. Regarding heat perception, it is air temperature, air movement, and radiant effects. In winter, you may feel colder facing an exterior wall or ceiling than with an extra room or story between you and the outside. Or facing a window versus having heavy drapes pulled shut. This is even if the air in contact with your body is the same temperature.
  - wolverine876 3y ago
    Thanks! One thing that works for me: I just turn the heat all the way off at night (or down to ~12 C to protect pipes, but I don't think it's ever gotten that cold inside). I just use more bedding if I need it - I'm generating 37 C, much warmer than desireable, so I just need to trap enough of that heat. Mornings are delightful, and my body retains the nighttime heat from the bedding (in its thermal mass, I suppose). Usually I don't turn on the heat until sundown.

wolverine876 3y ago

> modern roofing and DIY heat-rejecting window films What do you use? > nighttime ventilation and daytime closure I do that, it works very well (though depending on the house, of course), but I'm surprised I don't see it as standard advice for homeowners. Even better, an input at a cool spot (near shady grass, etc.), and output with an exhaust fan at the top; auto open/close based on thermostats outside and inside. > In winter, we heat to a more comfortable target for a few hours in early morning and after dusk. Is the early morning heat for efficiency somehow (or just it's too chilly when you wake up after an unheated night). - Also: Our perception is of it being colder when it's colder outside, despite the thermostat being set to the same temperature - that is, we need to set the thermostat a bit higher to not feel chilled. I wonder if our perception of temperature depends on something like the coldest (micro-)draft more than the ambient average.

saltcured 3y ago
It saves energy to let the house get colder overnight when we can rely on bedding to keep us warm. With a lower differential between indoors and outdoors, there is less total energy lost to the outside than if we held a constant target. I'm only dropping the set point about 5 degrees, not disabling heat entirely. Then the morning heat is to make it easier to get out of bed and start the day. We stop it again to take advantage of the common solar gain. But also, it doesn't take as much heat to feel comfortable once we've eaten and gotten more active for the day. For the roof, it is just one of the "cool roof" compliant asphalt shingle systems, with full plywood sheathing. We did not retrofit radiant-barrier sheathing, as there is fine print that this could overheat the shingles. As far as I can tell, the same performance to reject solar load in summer also reduces radiant loss in winter. Vaulted ceilings feel less exposed on a cold winter night. For windows, I applied Gila "heat control" film found at the local Home Depot. It is a modestly cool gray tint that looks only a little bit mirror-like from the outside, not too different from modern low-e glass. It takes a little practice to get satisfying results with the DIY application. I just used a spray bottle filled with tap water with a few drops of dishwashing soap, rather than any proprietary application fluid. Regarding heat perception, it is air temperature, air movement, and radiant effects. In winter, you may feel colder facing an exterior wall or ceiling than with an extra room or story between you and the outside. Or facing a window versus having heavy drapes pulled shut. This is even if the air in contact with your body is the same temperature.
- wolverine876 3y ago
  Thanks! One thing that works for me: I just turn the heat all the way off at night (or down to ~12 C to protect pipes, but I don't think it's ever gotten that cold inside). I just use more bedding if I need it - I'm generating 37 C, much warmer than desireable, so I just need to trap enough of that heat. Mornings are delightful, and my body retains the nighttime heat from the bedding (in its thermal mass, I suppose). Usually I don't turn on the heat until sundown.