Attic insulation (newbie content inside)
Alright, summer is here and the house is heatin’ up. I’ve noticed that our 2nd story is considerably warmer than the first. Duh, heat rises, but to what extent does the ‘hotter than hell’ attic above affect the temp of the 2nd floor, and what can I do to minimize this affect, if anything?
We’ve got a 2 story 1960’s Colonial in the Buffalo, NY area, and I’m wondering about the proper amount of insulation (and where to put it) and also the best way to vent the attic. Currently there is 1 layer of insul. between the ceiling joists and 1 vent on either end of the house.
Thanks,
Kyle
Replies
Oh you've come to the right place! Do a search for "vented attic" and you'll find a thread with ~ 100 or so posts from about a week ago.
Read through that and you'll be much more educated about the attic conditions!
In short... I'm going to foam my attic between the rafters and not vent it at all. I'm in Mass, about same conditions as you.
Stu
If you google for "insulation payback calculator" or something like that you will dig up a calculator that will give you payback on insulation installation. Not that payback is the only thing, but it is a data point. Insulation effectiveness is not linear. In other words, the first few inches are a lot more important than the next few inches and so on. If I recall correctly getting R-20 or so in your attic is a pretty reasonable point. I know we get all excited about R-5000 ceilngs, but at some point it's just useless.
What I would rather see is you sealing air leaks. Most likely your house is leaking quite a bit. That is likely pulling hot air into your house which immediately goes to the 2nd floor. But certainly you are taking some conductive heat from the attic (though the ceiling assembly).
I sometimes wonder why we don't make HVAC systems with dampers that can change where the majority of airflow is. I'd rather push 75% of my AC to the top floor and 75% of my heat to the bottom floor.
MERC.
You can do that; however, you will have to size the ductwork to handle the greatest amount of air that you might send through it. That would mean upsizing by 50% throughout in your example. Zone control dampers are then used to control the amount of air reaching the separate areas. It can be quite effective and costly.
My guess is most of the cost is in those automated damper control. I wouldnt' mind switching it manually, even if that meant jamming a partial piece or carboard in one trunk or the other.
MERC.
FYI, there are ductwork systems that will provide more air flow to various areas of the home. "Zone control" systems have been around for years.And another less costlier way would be to get more air flow into difficult areas via the "air balance " method.
See your local hvac tech.
One small nit picky thing. Remember that hot air rises, heat dissipates in all directions evenly. So you would need an air current to block the dissipation
Don't forget to leave your hvac fan to ON instead of AUTO. Leaving it to ON will help to prevent stratification of the cold air on lower levels and hot air on the uppers.
kevin
I'm in Ontario about 6 hours north of Buffalo but I've been down to your area to catch a wack of Sabres games and I know you get your share of snow. I have a 2 story and I put R60 in the attic. I have the cheapest heating bills of my friends with similar sized homes. If you have forced air heating try running your summer switch 24 hours a day to circulate the air in the house. If you have hot water heating you may consider a heat recovery ventilation unit to move the air.
It would not hurt to increase the ventilation in the attic.
Have a good day.
Cliffy
Edited 7/10/2005 12:17 am ET by cliffy