Almost Free Heat

[Question]

Does anyone else here use their attic heat in the in between seasons?

During Sept/Oct and Apr/May I **** the air out of my attic to heat my house and I also do it in my garage. My black roof faces south so it ***** up a lot of sun and radiant heat even on overcast days. I run an attic fan in the pull-down stairway to **** heat out of the attic and into the house/garage. I open a window at the far end of the house and the warm air blows thru the place and out the window. This seems to work as long as the outside temp is over 30 AND the winds are light, if its really windy it doesn't work. I'm usually able to raise the inside temp 3-5 degrees which is just enough during this time of year to take the chill out.

I put a piece of sona tube on top of the fan so it pulls air from near the top of the attic and block off the rest of the pull-down stair opening so that the air doesn't just short circuit. I find it works best after lunch till about 4pm.

So for the cost of the electricity to run the fan for a couple of hours I keep the oil man away for a few more days..

 

[Dragster Racer]

That is really clever. What is the air quaility up there though? Any smells or irritants that may be pulled into the house?

 

[rsanter]

you could install a round metal duct in the form of a loop. you can flow house air up and through and then back out into the house with a small fan. you would not need too much airflow as you want there to be enough time for heatsoak of the air

bob

 

[Question]

No real smell at all, the only thing up there is wood framing and insulation. Air enters under the eves and as it is heated moves up towards the peak and the ridge vent to exit, I grab it before it gets to the ridge vent. When I stand at the bottom of the stairs all I feel is warm air.

My wife doesn't complain about any smells and she sure has the sensitive noise... can smell a fart two rooms away....

 

[randydupree]

cool idea.i like it.

 

[stitch]

That's a great idea! It might also help cool the house in the summertime if you reversed the fan and pulled warm air from the house into the attic...

 

[Question]

I was able to raise the temp in the house by 4-6 degrees yesterday. Last night it was in the 40's but was comfy in here this morning without any heat.

Reversing it in the summer helps but you have to be careful about how humid it is outside, you don't want to bring in humid air.. Keeping the attic as cool as possible does help with the comfort in the house.

 

[Pritch]

I've been toying with this very idea. I have a 1100 sq ft single-sloped south facing black shingled roof that even on the coldest days heats the attic up quite a bit.

Here's what I will do:

Near the top (door end) of my shop I will put in 2] 16'' square electric fire/smoke dampers (I have these-leftovers from a job) These are normally closed and when powered, they open. At the other end, I will mount a ceiling mount exahust fan (I have this-leftover from a job) I think it says it moves about 500 cfm. I will wire the whole mess together with a line voltage thermostat that is placed in the attic. At a certain temp, the T-stat will send power to turn on the exhaust fan and open the fire/smoke dampers. All automatic, no muss no fuss. This would blow whatever heat right down in front of the blowers of my main heat system.

 

[Question]

Pritch, if your attic has soffet louvers you don't really need the damper. You want the air to rise up the inside of the roof to pick up the heat. If you get too much air just blowing thru the top it might not pick up enough heat. Give it a try without the dampers. You can always cut in later. Remember to wire the fan to the cooling terminals of the t'stat( to turn on when the temp is above X).

Another thing I do is to put a variac(also a job leftover) on the supply to the fan and adjust the fan speed depending on how hot it is in the attic.

Good Luck.

 

[Hardware]

. can smell a fart two rooms away....

Hey! More free heat

 

[mpraddict]

Just be careful about the type of insulation....some types have fibers you definitely dont' want to be breathing.

 

[Question]

If the fiberglass bats are installed properly with a barrier between the fiberglass and the underside of the roof, no air should be passing thru the insulation. The outside air passes between the underside of the roof and the barrier over the fiberglass, I have put a piece of plastic at the end of each bat so that cold air dozen't enter the bat, this is where there is a heat loss if you have ever seen thermo images of a ceiling. Anyways if you feel its a problem just put a furnace filter over the end of the intake pipe.

 

[mpraddict]

If the fiberglass bats are installed properly with a barrier between the fiberglass and the underside of the roof, no air should be passing thru the insulation. The outside air passes between the underside of the roof and the barrier over the fiberglass, I have put a piece of plastic at the end of each bat so that cold air dozen't enter the bat, this is where there is a heat loss if you have ever seen thermo images of a ceiling. Anyways if you feel its a problem just put a furnace filter over the end of the intake pipe.

If I understand this correctly you have plastic sheet on top of the batts? That is not the proper way to install them in your climate. It will trap moisture in the insulation! If you want a vapor retarder, it should be installed on the warm side of the insulation (between the insulation and the drywall).

 

[Question]

mpraddict, no the plastic is not on top of the bats, just at the end of the bat that hangs over the outside wall in the soffet, this is where the air does blow thru the bat if not blocked. I do have a vapor barrier installed as you described.