Attic insulation and open attic windows

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
Status
Not open for further replies.

mrjohneel

Feeling the Heat
Dec 8, 2011
275
Suburban Boston
I just re-insulated the attic in my 1928 house outside of Boston. It had 4" of old insulation under wood floor boards. I built some wooden platforms for storage, then laid down some 9" unfaced insulation under the platforms and over the wood floor. I have a hard foam insert covering the stairs leading to the attic. I don't have a ridge vent or soffit vents, so I was able to run the insulation all the way to the edge of the attic floor -- that is, I didn't have to leave a space for the air to travel up from the soffit. I have windows at either end of the attic. They have triple pane storm windows over them, so I left the screen window down and have both windows open a crack to get air circulating in the attic. (I even built a screen to go over the entire window on the inside of the attic just to make doubly sure no birds or animals poked through the window screen.) Here's my question: am I correct in leaving the attic windows open through the winter? The downstairs is warm; the attic is very cold. I think I need to keep the attic cold to prevent ice dams, etc. I don't have any other venting in the attic. No moisture (rain/snow) seems to be blowing in because of the eaves and the fact that the window is only open about 4-6". What do you think?
 

woodgeek

Minister of Fire
Jan 27, 2008
4,373
SE PA
did you airseal the attic floor before adding insulation?
 

mrjohneel

Feeling the Heat
Dec 8, 2011
275
Suburban Boston
The floor itself was covered with planking over the rafters; I didn't pull those up. But each space between the studs in the walls below the attic were sealed, as was the space around the chimney and bathroom vent. No recessed light fixtures.Should I keep the windows open?
 

midwestcoast

Minister of Fire
Oct 9, 2009
1,745
NW Indiana
So just to clarify, you have no attic ventilation at all? (no "mushroom" vents in the roof?). If so, and since you couldn't totally airseal, I'd leave them open some in the winter & fully the rest of the year. Make darn sure that bath vent (and any stove vent) is venting properly through the roof & not leaking into the attic. You don't want any moisture sources in there especially with little ventilation.
As to precipitation, need more info on the overhang or a pic.

If it were me I'd cut some vents in the roof come spring.
 

mrjohneel

Feeling the Heat
Dec 8, 2011
275
Suburban Boston
Thanks. No mushroom vents or those louvered vents you see at each end. Instead I have the windows. The bathroom fan is vented correctly out of the roof. I went up after a big rain and surprisingly there wasn't any rain collecting in the attic. But it is an open window so I have concerns.
 

dave11

Minister of Fire
May 25, 2008
632
Western PA
Was there ever any proper attic venting? Did someone remove it? No gable vents at all?

If so, you should keep the windows open both winter and summer. The attic needs to be as close to the outside temp as you can get it, year round.
 

mrjohneel

Feeling the Heat
Dec 8, 2011
275
Suburban Boston
I have old photos of the house and it has always been like it is: it is two stories with the attic on top of that. Rather than gable vents, it has two small windows. (Nice view over all the other houses!) I've been here seven years through some tough winters. No ice dams, no mold. But I had to get some serious insulation up there though to cut down on my $3700/yr. oil bill. (Close to inserting a Harman P35! pellet stove.) I'll keep the windows open.
 

woodgeek

Minister of Fire
Jan 27, 2008
4,373
SE PA
Since you are reasonably airsealed you don't NEED attic ventilation in the winter, but a little is always good insurance. It will always help dry out any moisture that does get in, e.g. through the gable siding, diffusing through the roofing, etc. And reduce the chances of ice dams, as you said.

I think you are in good shape with what you are doing. In the summer, you might want more ventilation just to reduce temps/AC costs, but that was not your question. A thermostatic window fan in one window might be a cheap/easy sol'n.
 

maple1

Minister of Fire
Sep 15, 2011
10,783
Nova Scotia
I think you definitely DO NEED attic ventilation, all year round.

From your description in your second post, it sounds like you're not air sealed - or at least don't know for sure. I only see mention of spaces between wall studs, and a couple of other spots. That would mean there is not much stopping warm moist air from getting up there from below.

And even if it was air sealed, attics require ventilation.

Sounds like you're doing OK with the opened windows, just keep an eye on things, especially during snow storms - that stuff can blow in the smallest of cracks, in large amounts, if the wind happens to line up the right way.
 

woodgeek

Minister of Fire
Jan 27, 2008
4,373
SE PA
maple1, I agree with you. I was taking his years with no ventilation AND no problem (mold/dams/etc) as a sign that he had adequately airsealed, and/or the attic was already 'breathing' enough to take care of whatever H2O came through.

In general, though, you are right, one does not want to mess with underventilating an attic.
 

midwestcoast

Minister of Fire
Oct 9, 2009
1,745
NW Indiana
The reason I said open just a bit in winter is 'cause snow can/will swirl around & get in places where rain won't. Would that add any significant moisture to the attic? No idea.
The insulation you added & air sealing is your best defense against ice dams. Opening those windows would likely have little effect on attic temps since there's no heat source up there & no insulation to the outside.
 

Grisu

Minister of Fire
Nov 1, 2010
4,121
Chittenden, VT
If you are concerned about snow/rain coming in I would put some old towels on the windowsill inside and maybe at the floor right under the window with some plastic underneath and check them occasionally. They will certainly limit the damage should water come inside.
 

Flatbedford

Minister of Fire
Mar 17, 2009
5,252
Las Vegas, NV
I have a similar situation. There are no vents in my attic either. I asked a roofer friend about installing a ridge vent. He said to leave the windows open a bit and don't bother with the vent. My attic is not that well air sealed so I have to be careful about moisture getting properly vented.
 

rwhite

Minister of Fire
Nov 8, 2011
1,800
North Central Idaho
No vents in the soffits of my old home either but I bet if you get up there in the dark you can find some light coming through somewhere. I can't cant say enough about the mushroom turbine vents I put on the roof though. I have a room in the attic and it lowered the temps up there 20 degrees in the summer.
 

Don2222

Minister of Fire
Feb 1, 2010
8,780
Salem NH
Hello

The short answer is Yes, you need to keep them open.

The long answer is that your house will be much warmer in the winter if you do add soffit venting and ridge venting and then close the windows.

I am just north of you and I originally just had gable vents. So when the roof was re-done they added the ridge venting and I added the soffit venting after.

So then I put in the rafter vents from the soffits all the way up to the ridge vent and stappled Home Depot Reflectix Foil over the rafter vents.

Now the foil keeps the whole house 10 degrees cooler in the summer.

Then if I close up the gable vents in the winter the whole house stays 10 degrees warmer.

That cuts my heating and cooling costs by at least 20 percent!!!!! $$$Cha-Ching$$$

It is a difference you can feel!!
 
Status
Not open for further replies.