Using attic heat for the house - Page 17

Exeric · 10-26-12, 08:31 PM

I thought i'd fill you all in on what became of my ambitious plans to use attic heat to heat the house. Unfortunately I've discovered a big rodent problem in the attic. I can get rid of them but there will always be the potential problem of blowing dust from old rat poop into the house. Not good. I could use a filter but human nature being what it is there would always be times when it either gets clogged or was not replaced once when it was taken out for cleaning, either by me or a new owner. Its a problem just waiting to happen down the line. So I've decided to abandon the idea for health reasons.

A side issue in abandoning the idea is that my roof is prime real estate for putting up future solar panels. If that ever happens they would absorb or reflect much of the heat the roof would get, thereby diminishing the effectiveness of attic heat. I think attic heat is a good idea but after much thought I think it best to design it into the construction of the house to begin with. That way one wouldn't have the rodent problem to deal with or solar panels diminishing it's effectiveness.

Exeric · 10-26-12, 08:43 PM

Btw, I'm still planning to put up radiant foil insulation attached to the underside of the rafters to reduce the heat load in the attic in summer. That, and two whole house fans I bought, should keep the summer heat under control without excessive use of air conditioning.

ecomodded · 10-26-12, 09:25 PM

If any attics have fiberglass insulation like my attic does the particles could be cancerous in the long run, I used a box fan in my attic hatch this summer on a few occasions when i had it turned off a back draft would blow the attic insulation smelling air back into the house. Next year i am going to make a cover for the fan for when its turned off.

Exeric · 10-26-12, 10:05 PM

Quote:

Originally Posted by ecomodded

If any attics have fiberglass insulation like my attic does the particles could be cancerous in the long run.

Yeah, just another issue I would have to deal with. In a closed vs open system contest a closed system wins easily.

Daox · 10-31-12, 01:07 PM

I thought I'd give an update on my system as well. Its been working without any issues this fall. However, its been very windy as well, and therefore the attic hasn't been getting very warm. So, it hasn't provided as much heat as it has in the past.

Exeric · 11-06-12, 11:51 PM

I had a thought after running into problems with air contamination using attic heat and diminishing attic heating problems if one installs solar panels on the roof. It isn't all thought out yet but it is similar to Xringer's idea of using attic heat to heat his basement.
Basically this idea wouldn't work unless you have a crawl space that you have converted to a heated and sealed crawlspace.

Generally, to insulate a house it is advised that one also insulate the bottom floor. It depends on the structure of the house but in my case i have a crawl space over the main floor. There are two ways of doing it - either directly, or indirectly by sealing the crawl
space and making it part of the conditioned structure. You would have to leave the floor uninsulated in that case.

I decided for my case, others may feel differently, that it is better to not use an open system for the air heating. But there are closed solar collectors that you can build for air just like for water and supposedly they are about 40% efficient. The only drawback of air versus water is that it usually takes a lot of engineering to build a heat reservoir for warm
air. A sealed crawl system seems like the perfect thing to use as a heat reservoir in winter that that doesn't cost gobs of money and engineering.

I learned a lot about this from reading an older book: "Solar Air Heating Systems", by Kornher and Zaugg. This seems like a really good approach to me. I know what you are thinking: doesn't that just reintroduce air contamination problems from the crawl space?Not really. At least not if you don't use fiberglass AND you seal down a fresh layer of plastic on the ground after you get rid of any rodents or bugs. You'd go this route anyway if you opted to bring the crawl space into the conditioned area so it really shouldn't be that expensive to go this route over just insulating the floor.

Anyway, the beauty of this is you could just open up some registers at night to get more heat from below if natural conduction and radiation of heat from below wasn't enough. I'm just thinking out loud about this right now and would appreciate any constructive criticisms, even if it would end up convincing me to not work on the idea. Obviously this most likely wouldn't work with a basement as a substitute because you'd probably end up overheating it. You don't actually live in a crawlspace, at least I hope you don't.

Exeric · 09-02-13, 07:55 PM

I decided to revive a long dead thread with some interesting news. I have been working on the attic air heating idea and have done most, but not all, of the construction on it. It uses an open system after all, but where the air enters the vented roof through baffles at the eaves a radiant foil barrier comes down to meet it. This way a thin layer of pretty hot air moves up between the rafters without danger of insulation contamination. Also there is a readily accessible place to change the filter down in the occupied living area. I will be posting pictures soon.

This is a designed from the bottom up system so if if doesn't end up making financial sense here in a moderate climate - California - then it won't make sense anywhere. Having said that, the project is not yet completed, nor have I yet experienced a winter with the system complete, so only time will tell how effective it is. I promise to show you any problems with the system over time and won't keep you hanging if it turns out not to have have been a good idea.

I will start a new thread with this information, including construction photos soon, and will post a link to the new thread when I put it up.

Xringer · 09-02-13, 09:05 PM

Thanks for updating us on your efforts. I'm still crazy about the idea..
Not sure how many BTUs I could harvest from my attic,
but any amount would be better than zero.

I am currently able to pump cold air out of my basement.
Adding an air duct from the attic would be the next step..

Daox · 09-03-13, 08:10 AM

Very cool Exeric. I'm looking forward to seeing your setup!

MWinfrey · 09-08-13, 04:43 PM

How about adding a duct that runs from the highest part of the attic to the return air vent of your HVAC system. That gives you the filtering of the attic air and also distributes that warm air to the entire house. Would need to be able to block this hot air when you are using the air conditioner or when heating is not necessary.

10-31-12, 01:07 PM	#165
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	I thought I'd give an update on my system as well. Its been working without any issues this fall. However, its been very windy as well, and therefore the attic hasn't been getting very warm. So, it hasn't provided as much heat as it has in the past. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

09-02-13, 09:05 PM	#168
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	Thanks for updating us on your efforts. I'm still crazy about the idea.. Not sure how many BTUs I could harvest from my attic, but any amount would be better than zero. I am currently able to pump cold air out of my basement. Adding an air duct from the attic would be the next step.. __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less..

09-03-13, 08:10 AM	#169
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Very cool Exeric. I'm looking forward to seeing your setup! __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

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10-26-12, 08:31 PM	#161
Exeric Apprentice EcoRenovator Join Date: Aug 2012 Location: California Posts: 274 Thanks: 19 Thanked 37 Times in 28 Posts	I thought i'd fill you all in on what became of my ambitious plans to use attic heat to heat the house. Unfortunately I've discovered a big rodent problem in the attic. I can get rid of them but there will always be the potential problem of blowing dust from old rat poop into the house. Not good. I could use a filter but human nature being what it is there would always be times when it either gets clogged or was not replaced once when it was taken out for cleaning, either by me or a new owner. Its a problem just waiting to happen down the line. So I've decided to abandon the idea for health reasons. A side issue in abandoning the idea is that my roof is prime real estate for putting up future solar panels. If that ever happens they would absorb or reflect much of the heat the roof would get, thereby diminishing the effectiveness of attic heat. I think attic heat is a good idea but after much thought I think it best to design it into the construction of the house to begin with. That way one wouldn't have the rodent problem to deal with or solar panels diminishing it's effectiveness.

10-26-12, 08:43 PM	#162
Exeric Apprentice EcoRenovator Join Date: Aug 2012 Location: California Posts: 274 Thanks: 19 Thanked 37 Times in 28 Posts	Btw, I'm still planning to put up radiant foil insulation attached to the underside of the rafters to reduce the heat load in the attic in summer. That, and two whole house fans I bought, should keep the summer heat under control without excessive use of air conditioning.

10-26-12, 09:25 PM	#163
ecomodded Supreme EcoRenovator Join Date: Sep 2012 Location: Vancouver Island,Canada. Posts: 1,037 Thanks: 116 Thanked 100 Times in 87 Posts	If any attics have fiberglass insulation like my attic does the particles could be cancerous in the long run, I used a box fan in my attic hatch this summer on a few occasions when i had it turned off a back draft would blow the attic insulation smelling air back into the house. Next year i am going to make a cover for the fan for when its turned off.

11-06-12, 11:51 PM	#166
Exeric Apprentice EcoRenovator Join Date: Aug 2012 Location: California Posts: 274 Thanks: 19 Thanked 37 Times in 28 Posts	I had a thought after running into problems with air contamination using attic heat and diminishing attic heating problems if one installs solar panels on the roof. It isn't all thought out yet but it is similar to Xringer's idea of using attic heat to heat his basement. Basically this idea wouldn't work unless you have a crawl space that you have converted to a heated and sealed crawlspace. Generally, to insulate a house it is advised that one also insulate the bottom floor. It depends on the structure of the house but in my case i have a crawl space over the main floor. There are two ways of doing it - either directly, or indirectly by sealing the crawl space and making it part of the conditioned structure. You would have to leave the floor uninsulated in that case. I decided for my case, others may feel differently, that it is better to not use an open system for the air heating. But there are closed solar collectors that you can build for air just like for water and supposedly they are about 40% efficient. The only drawback of air versus water is that it usually takes a lot of engineering to build a heat reservoir for warm air. A sealed crawl system seems like the perfect thing to use as a heat reservoir in winter that that doesn't cost gobs of money and engineering. I learned a lot about this from reading an older book: "Solar Air Heating Systems", by Kornher and Zaugg. This seems like a really good approach to me. I know what you are thinking: doesn't that just reintroduce air contamination problems from the crawl space?Not really. At least not if you don't use fiberglass AND you seal down a fresh layer of plastic on the ground after you get rid of any rodents or bugs. You'd go this route anyway if you opted to bring the crawl space into the conditioned area so it really shouldn't be that expensive to go this route over just insulating the floor. Anyway, the beauty of this is you could just open up some registers at night to get more heat from below if natural conduction and radiation of heat from below wasn't enough. I'm just thinking out loud about this right now and would appreciate any constructive criticisms, even if it would end up convincing me to not work on the idea. Obviously this most likely wouldn't work with a basement as a substitute because you'd probably end up overheating it. You don't actually live in a crawlspace, at least I hope you don't.

09-02-13, 07:55 PM	#167
Exeric Apprentice EcoRenovator Join Date: Aug 2012 Location: California Posts: 274 Thanks: 19 Thanked 37 Times in 28 Posts	I decided to revive a long dead thread with some interesting news. I have been working on the attic air heating idea and have done most, but not all, of the construction on it. It uses an open system after all, but where the air enters the vented roof through baffles at the eaves a radiant foil barrier comes down to meet it. This way a thin layer of pretty hot air moves up between the rafters without danger of insulation contamination. Also there is a readily accessible place to change the filter down in the occupied living area. I will be posting pictures soon. This is a designed from the bottom up system so if if doesn't end up making financial sense here in a moderate climate - California - then it won't make sense anywhere. Having said that, the project is not yet completed, nor have I yet experienced a winter with the system complete, so only time will tell how effective it is. I promise to show you any problems with the system over time and won't keep you hanging if it turns out not to have have been a good idea. I will start a new thread with this information, including construction photos soon, and will post a link to the new thread when I put it up.

09-08-13, 04:43 PM	#170
MWinfrey Lurking Renovator Join Date: Sep 2013 Location: TX Posts: 1 Thanks: 0 Thanked 0 Times in 0 Posts	How about adding a duct that runs from the highest part of the attic to the return air vent of your HVAC system. That gives you the filtering of the attic air and also distributes that warm air to the entire house. Would need to be able to block this hot air when you are using the air conditioner or when heating is not necessary.