Hi guys. My wife and I are in the late planning stages of building
our new home. I want it to be as energy efficient as possible. We
are having a slight disagreement.
I want foam insualtion in walls and attic. She is ok with that. What
we disagree about is how to do the attic.
Her ex-husband is a HVAC contractor. He says we should use the " foam
the underside of the roof, seal the attic and semi condition it"
method. Our builder agrees.
My problem with that is, why would I want to semi condition an area
the same size as my house if I am never going to use it for anything?
I want to foam the attic floor, and make sure the attic is well
venitaled. Why is allowing my warm and cold air (that I am paying to
heat and cool) to migrate up into my attic a good idea? Isn't it more
efficient to keep that expensive air in the house by well insulating
the attic floor?
Can anyone give me advice on why my thoughts are wrong?
Are you going to use the attic for storage? Depending on where you
live and the local climate, anything you store in the attic could
be damaged by temperature extremes. I've seen some very large attics
that were an incredible waste of space, is yours one of those?
Haven't planned on using it for storage. We will be building about 60
miles north of Dallas. That's why the though of semi conditioning
that space sure seems wasteful. And we get pretty dang cold in the
winter and I hate the thought of my warm air going through the ceiling
into an attic that isn't used for much.
You are right you will be heating the attic from migrating heat loss
up, the builder will be happy to agree since it will take more foam,
more foam means a bigger job, more money. If you are foaming
everything you are including a heat recovery ventilator for that tight
Then You AC pro aint no pro because a fomed house is like living in a
foam cooler, its doent breathe or have enough air exchanges per hour
to keep you healthy, google overtight houses that dont breathe, sick
house syndrome, do research now and maybe hire an architech because
several ideas you plan dont make sense, maybe alot more dont.
It was just a casual conversation with my wifes ex about the house,
not a detailed planning session, he wont be the HVAC contractor. i'n
just getting ideas.
I think the expression is Build it Tight, Ventilate it Right.....
I added glass wool insulation to the attic floor *and* roof joists, and what
Ahm no spert, but I think ventilating a tight house is not nearly as
difficult as making it tight.
I'm reminded of an acquaintance up in Mass. who read something about
"ventilated attics", and promptly hole sawed/sawzalled about 400 holes at
the base and outside of her attic!!!
Sure makes insulation moot, dudnit?????
I fought like crazy against this idea, to no avail.
I don't know how she's doing with all those effing holes, but I did detect
the onset of some grumbling....
Might as well just open all the windows in winter, while she's at it!.
You have winters in Dallas???? For how long, and how cold?
Oh, a note on attics:
If the attic is such that you can stand up in it and walk around, they can
become pretty useful from a variety of povs.
It helps to have a *good* drop-down staircase going up, and decent lighting.
They can be neat work-spaces for light things like sewing, etc, made into
neat play areas for kids, even serve as infrastructure for things like A/C,
warehousing inventory for a home business, etc.
We added almost 1,000 useful sq ft to the house by just insulating, throwing
down some plywood, and unrolling some cheap commercial carpet, adding some
fluorescents along the apex. No heat necessary, not too bad in the summer.
However, a fully finished attic(for living) likely violates code, or will
require a permit.
I gotta go along with the others who say insulate the attic floor. From
what I have heard, foaming the rafters (underside of the roof) can cause
high humidity/condensation problems in the attic. I would use radiant
barrier roof decking and plenty of attic ventilation. You can reach a
point where slight gains in overall thermal efficiency can cause major
side effects that offest any savings exponentially. Larry
iirc, Silva on Ask TOH did a very inneresting ditty on insulation (esp.
spray insulations) very recently, and goodgawd, does it get complicated!
And it went by pretty fast, something you would def'ly want to take notes
For example, the vapor barrier goes on different sides, depending on yer
In mixed climates, there are additional "breathable" barriers you can use.
Would be useful to catch that episode, don't know if the TOL has it.
Seems to me a double-layered roof, with a 2-4" air gap, with continuously
circulating air, and then the bottom layer super-insulated
(anything/everything) on the attic side would be a permanent solution.
But I've never heard of a double-layered roof, which seems simple enough to
do, just some extra plywood/2x4's.
I'm considering just living in a tent....
Double layered roof is what you get when you put Spanish tiles on a
roof. The air can flow under the tiles. You get the same effect more
or less by putting foam insulation underneath the decking with an air
space between the foam and decking.
WTF, you allow her EX to put in his 2 cents! Thats your problem, ban
him. Even worse, he is an AC contractor not contracting.
If he's anything like the cretins on alt.hvac, she's proly paying HIM
Or at least giving him a beer allowance.....
1. Foam the underside of the roof? If you do that, the shingles will melt.
Well, maybe not melt, but they will surely degrade rather quickly.
2. The almost unanimous advice, I'll bet, of the experts and knowledgeable
amateurs here is that you will rue the day you go against the wishes of the
lady of the house. Hereafter, EVERYTHING that goes wrong will be attributed
to your hair-brained decision on the attic. I'm talking stopped-up toilets,
mice in the pantry, windows that won't close, psoriasis, and the refusal of
the grocery clerk to take coupons for stuff your wife didn't buy.
How bout regular bats (glass wool) of insulation?
Proly doesn't apply to slate.
Suggests making a kind of double roof, for air flow beneath the shingles!
Then the joist gap in the attic can be foamed.
> > 2. The almost unanimous advice, I'll bet, of the experts and knowledgeable
My neighbor has a cathedial ceiling poorly vented with just regular
insulation, his 35 years shingles only last 5-6 years in S. exposure,
yup, heat kills and so do a wifes ex that you stupidly allow to get
within 100 feet or give info on money decisions.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.