Insulation question

muncybob

Our house is old...the attic roof is supported by round hand hewn timbers that are about 4" in diameter. The roof is very old metal standing seam and some of the under side of the metal is exposed. In the winter warm air causes condensation to form and drip onto the attic floor. Other than 2 small windows in each gable, there is no ventilation up there....no ridge vent and no ventilation in the soffits.
I was told I should seal off the attic windows and spray 3 to 4 " of closed cell foam onto the under side of the roof. Also to apply an inch or so onto the gable walls. The attic would then be without any ventilation which concerns me somewhat. Any insulation experts out there want to weigh in on this?

GlennDog

Just curious, where are you located? New England?

Regardless of location. Start with an experienced contractor that air seals/insulates based on his findings

when using a blower door test.

This is the only way to go, IMHO

mhardy6647

The goal is to keep the attic cold in the winter time. Northern New England is famous for ice dams in the winter time, forming in attics that aren't properly insulated from the warmth of the house below 'em. Standing seam roofs should preclude the problem of ice dams, but a warm attic will still tend to be problematic in a cold winter climate, I would think.

Obviously, the calculus is different if you have living space in the attic. The advice cited in the OP seems to be for an occupied attic? I am no expert but I think ventilation is key to solve the problem in the OP, unless the attic is to be occupied by humans in the winter time.

Massachusetts has a terrific energy program that will do a comprehensive (and free) assessment of the home, provide a list of recommendations and cover a big percentage of the costs of the work (90%, when we did it). We had this done at our old house in MA and it was a fantastic bargain.

Based on our experience (and here in Northern New England, at least) there should be soffit vents with a clear path for the cold air to be drawn in from outside at the 'base' of the attic, and (in most cases) a ridge vent or some other vents at the "top" of the attic for convection. In terms of attic insulation, blown in insulation (between the joists, not up in the rafters) seems to be the thing nowadays. Another important thing is to seal the tops of any walls that contact the attic, otherwise, they can act as chimneys, bringing warmer air from below up into the attic. If you have an attic scuttle, be sure that sucka is insulated (or has an insulated tent or canopy over it), otherwise, as the late Frank Carpenter @ AK said to me, " it's just a window to the outside world" from an insulation standpoint.

I definitely concur, work with good contractors who know what they're doing (and who've been doing it for a while).

DaveHo

The correct solution is to add proper ventilation. By insulating the underside of the roof & sidewalls you are basically making the attic part of the house envelope. Is there insulation on the attic floor? If there is, I think that will cause problems.

mrbiron

All good comments, especially Hardy’s opening sentence.

Like mentioned above, is this a finished attic?

If not;

I would start with a metal roof installer and find out if he can do a ridge vent. Most likely can. Do you have eave vents? Make sure they aren’t clogged with insulation or debris in the screen. Air should circulate up the eave vent and force hot air out the ridge/gable vent. Attic soffit vent will allow you to blow insulation to the ends of your rafters while still allowing this airflow.

Start there.

muncybob

We live in Pa., comparable to New England(lived there too, NH). Attic is storage only but has a t&g wood floor that is insulated somewhat. The roof structure is not typical truss but the mentioned "logs" that are nailed/fastened together. I'm not sure how a ridge vent could be cut in without causing problems and without eave ventilation I think it would not solve anything.

Maybe I should get an estimate on eave/soffit ventilation, verify if a ridge vent can be installed or not and keep the gable windows open all year long?

motorhead43026

Soffit vents and wind turbine vent.

mhardy6647

Vents like this would (could) work OK in lieu of a ridge vent -- couldn't they?



I mean, I'm a biochemist, so I am a little out of my depth here.

heh -- good ol' the internet...



I dunno about pressurizing the attic, but the general airflow stuff in that image looks OK to me (aforementioned biochemist, not contractor/energy consultant)

muncybob

Both gables have vents like your pic shows there doc. The turbine vent crossed my mind but more than 1 person said it would not correct the situation.

Emlyn

Passive air flow seems best to me. Fitting a too strong powered solution to extract air from the attic space would likely draw heat or conditioned air by force up from the house as old houses were not sealed for that type of system. Could make the situation worse if it’s not done by a good pro who knows how to work with older construction. Spraying foam all over everything has led to big problems in a lot of cases from what I’ve heard.

Adequate air flow but not too much is key.

mrbiron

whether you have dimensional lumber or logs, there has to be a nailing Substrate on top of your rafters. The substrate is cut back so air can flow past your ridge beam.

Maybe a photo will help...?

delkal

Can't help with the insulation issue but you should make sure any bathroom fans are vented to outside and not just venting the humid air into your attic. I had moisture problems and some rotten plywood because of this.

mhardy6647

delkal wrote: »

Can't help with the insulation issue but you should make sure any bathroom fans are vented to outside and not just venting the humid air into your attic. I had moisture problems and some rotten plywood because of this.

yup (even in cold climates) -- there are vent fans made for this that still maintain reasonable energy efficiency.

txcoastal1

Went through this when we purchased and old duplex in Galveston and converted it to a single living house and installed central air. We had the option of sealing the attic and using the foam on the roof. Almost went that route until we were reminded that if you choose, that if ever a roof leak it becomes a nightmare to locate the leak. If you the roof needs to be replaced then there is the foam repair in both cases.

We opted not to do it especially being in a hurricane zone

shawn474

This is from experience....when we bought our home the insulation was woefully inadequate. They agreed to add insulation and us being young and dumb accepted that they were going to do it right. Ends up they just added a Layer or roll insulation- fast forward six months and found out while cleaning gutters that the roof was soft and almost stepped through it. They had covered our soffit vents and restricted air flow. Moisture built up from inside the attic and rotted the roof from the inside out. Best advice is hire an expert - it’s worth it compared to the little cost you will save trying to do it yourself