Idea for a solar "wall"

Topher Belknap wrote:
1) As others have said, insulation and air sealing is usually a better place to start.
Yes coupled with the addition of an HRV would also help keep things efficient, comfortable, and healthy
2) Air sealing (especially if you plan to run your house at positive pressure) is important, as you don't want to be pumping warm moist air into your walls where it will condense, and encourage rot.
If your less permeable barrier is to the inside of the wall this should be a non issue. Walls should breath to the outside.
4) Positive pressure is not a solution for infiltration. It just becomes exfiltration.
Indeed, why would you want your building to to do either?
5) You are going to want the woodstove when the sun isn't shining, so the solar heater won't be in service.
Yes, I've battled with this problem myself... How can I get solar gain at night? The only solution I know of is thermal mass (anti Knight flame suit on...)

Thank You Kindly,
Topher

Sean Rauch wrote:Few comments in red

Topher Belknap wrote: and replied in green
2) Air sealing (especially if you plan to run your house at positive pressure) is important, as you don't want to be pumping warm moist air into your walls where it will condense, and encourage rot.
If your less permeable barrier is to the inside of the wall this should be a non issue. Walls should breath to the outside.
A low-permeability barrier is all well and good, in the appropriate climates. But a) It doesn't do anything to reduce infiltration through holes, which are the vast majority of the air sealing failures. b) It is usually not something homeowners of existing homes have a lot of control over. (or perhaps more accurately, want to take control of) c) Drying to the outside is no substitute for not letting moisture into the walls in the first place, d) Is not a good idea in certain climates.

Thank You Kindly,
Topher

Topher Belknap wrote:

Sean Rauch wrote:Few comments in red

Topher Belknap wrote: and replied in green
2) Air sealing (especially if you plan to run your house at positive pressure) is important, as you don't want to be pumping warm moist air into your walls where it will condense, and encourage rot.
If your less permeable barrier is to the inside of the wall this should be a non issue. Walls should breath to the outside.
A low-permeability barrier is all well and good, in the appropriate climates. But a) It doesn't do anything to reduce infiltration through holes, which are the vast majority of the air sealing failures. b) It is usually not something homeowners of existing homes have a lot of control over. (or perhaps more accurately, want to take control of) c) Drying to the outside is no substitute for not letting moisture into the walls in the first place, d) Is not a good idea in certain climates.

Thank You Kindly,
Topher

Sealing a wall either from both sides equally or more to the outside is a bad idea all round. Summer humidity should be fine because you won't have a dew point for the moisture to become liquid inside the wall system you want a certain amount of "acclimatization" between your wall and the outside conditions. Where things go sideways is when you have a less permeable surface on the exterior that can get cold enough for interior humidity to condense against during the winter. Winter is where you get humidity condensing and rotting out the inside of your wall system.

Sealing up holes should have zero effect on this one way or another.

If the owner's issue is not enough insulation overall then they will want to address insulation for the entire envelope, however that looks. If there is enough insulation and its just air leakage through services, windows, doors etc then seal up the holes, its a no brainier. Purposely having air move unrestricted into the wall system from inside the house is your worst case scenario.

Sean Rauch wrote:Summer humidity should be fine because you won't have a dew point for the moisture to become liquid inside the wall system

Winter is where you get humidity condensing and rotting out the inside of your wall system.

Sealing up holes should have zero effect on this one way or another.

Purposely having air move unrestricted into the wall system from inside the house is your worst case scenario.

Creighton Samuiels wrote:I don't think some of you quite understand what I'm trying to do. I don't have a well sealed home, as it's about average for a house build for it's era (1970's), and I don't particularly want a well sealed home. Well sealed homes in my (very damp) climate tend to have mold issues.

This house has plenty of gaps that slight positive pressure isn't going to be pushing through wall structures

and the heated winter air would be VERY dry, also a goal.

Delayed heat gain can be accomplished by putting baby food jars of candle wax inside the plenum air spaces of the solar wall, allowing the draft of the nighttime woodstove fire to draw make-up air past the jars of melted wax for as long as that heat lasts.

prevent my propane central forced air furnace from turning on.

Topher Belknap wrote:

Creighton Samuiels wrote:I don't think some of you quite understand what I'm trying to do. I don't have a well sealed home, as it's about average for a house build for it's era (1970's), and I don't particularly want a well sealed home. Well sealed homes in my (very damp) climate tend to have mold issues.

I think I do understand what you are trying to do. I just have ideas about the way that I think you ought to do it. A well sealed, properly ventilated house, is by design less likely to experience mold issues. With one you are trusting to passive moisture and air movement, and with the other you are controlling both. It is true that many well sealed houses neglect proper ventilation, and thus have mold issues; that is a failure of execution.

and the heated winter air would be VERY dry, also a goal.

If the air is VERY dry, where did all the water go?
I am not a medical professional, but I worry about extremely low humidity from a health perspective.

Delayed heat gain can be accomplished by putting baby food jars of candle wax inside the plenum air spaces of the solar wall, allowing the draft of the nighttime woodstove fire to draw make-up air past the jars of melted wax for as long as that heat lasts.

Store heat inside the building, not in the collector, would be my recommendation. I don't think baby jars worth of wax, are going to be enough heat storage.

prevent my propane central forced air furnace from turning on.

I maintain that you are going to need that propane furnace much more with all those leaks in your house. I see 20-50% of heat loss of houses attributable to air leakage, it might be similar in your region. How many complete air changes do you need per hour?

Thank You Kindly,
Topher

Creighton Samuiels wrote:Are you saying that I shouldn't err on the side of a heated positive pressure? If I had some way of detecting such a mild negative pressure as caused by the exhaust from the woodstove or furnace, I'd probably do that. Perhaps just not have a blower at all, but just a passive design?

Winter air is dryer, because it's temp is below the dew point and the moisture condenses out. Then my solar wall heats that air above 90 degrees, and blows it into my (otherwise usually damp) basement space. The incoming air is dry, the air in the house generally is not; I'm mixing them up to get a dryer winter balance.

I pull a gallon of water a day from them in the dead of winter here. Seriously, if you've never lived in Kentucky, you really can't imagine what it's like. There really isn't a dry season.

However, due to another thread regarding heat storage using phase change materials, I know that candle wax makes an excellent heat battery.

Mostly I need dryer air more than air exchanges per se, but air exchanges work towards that end during the heating season.

I only want the fan to blow when the solar panel is above 90-100 degrees, so the idea that I'm losing heat by pushing a volume of 70 degree air out of the home using 90 degree air doesn't logically follow, and for some portion of that time that 70 degree air is being pushed out through a combustion chamber, not walls or windows, anyway. I intend to fix the air leaks that can be (economically) fixed anyway, but there will still be some that cannot be fixed.

Topher Belknap wrote:

Creighton Samuiels wrote:However, due to another thread regarding heat storage using phase change materials, I know that candle wax makes an excellent heat battery.

Candle wax has a melting point that is too high for optimal heat storage, preferably you want something with a melting point at room temperature. There are some special wax mixtures which do that.

Mostly I need dryer air more than air exchanges per se, but air exchanges work towards that end during the heating season.

You might also want to consider a HRV (Heat Retaining Ventilator), given your location, someone will no doubt try to sell you an ERV (Energy Retaining Ventilator) but that would retain the humidity that you want to get rid of. Crank that sucker up on cold days, and you could reduce the humidity substantially, while retaining 85% or so of the heat.