Attic insulation - need advice

[Murdoc]

Last summer I bought an 1000 sq ft colonial that was built in the 1920's.

It has about 2 inches of old fiberglass bats covering the attic floor. It has no soffit vents but there are three roof vents.

The roof was constructed using rough cut 2x4 rafters instead of the more typical 2x6 construction:





Also, the roof line actually comes down into the second floor living space:





This creates a cavity about 4 feet long and 4 inches high from the edge of the attic floor to the eave:




This winter was particularly severe and there was lots of ice damming around the roof.

An insulation contractor came over last week and gave an estimate on improving the insulation in the attic. He recommended completely filling in the cavity with either spray foam or dense packed cellulose and blowing in cellulose in the rest of the open attic space. He said that because of the way the roof is constructed, there isn't a lot of room to work with, and it isn't worth adding soffit vents. He also said that there will always be some ice damming no matter what is done, but filling the cavities would cut down on it a lot.

I'm worried about mold and rot becoming a problem doing it this way without the soffit vents. Adding the soffit vents, baffles, and 2.5 inches of spray foam would cost about $900 more than just using dense pack cellulose and still not give a much better R-value than dense pack cellulose (about R-15 to R-17).

I'm having another insulation contractor look at it tomorrow, but I'd like some of your opinions.

What do you guys think?

 

[stormkroe]

Is there no insulation in all the 45° spaces or did you dig it out of the one in the picture?

 

[Greenman]

I'm not very knowledgeable about ventilation in snow country, but here in sunny California, if we can't ventilate an attic space it has to be packed full of insulation. Foam would be best, dense pack cellulose would probably work. The idea is to move the condensation point out onto the roof surface, so the insulation has to be tight against the inside of the roof.

Get a reputable contractor and listen to him.

 

[TheSlamma]

With that limited amount of insulation and venting you are most likely always going to have ice dams.

The only way to deal with it without a new roof or adding more venting is to use heat tape (your gutters are probably ice blocks right?), you can buy gutters now that actually have it built into the leaf guard or you put it up every fall and take it down in the spring so the sun doesn't destroy it.

Your other option is most new code requires a Water and Ice shield they put for the last 36 inches, it's a membrane just for ice damming. But of course that means new roof.

 

[Murdoc]

Is there no insulation in all the 45° spaces or did you dig it out of the one in the picture?

No, there's no insulation in any of the 45 degree spaces.

 

[Murdoc]

Well, I had another contractor look at it today. He recommended the same thing that the other contractor recommended - dense pack cellulose in the sloped parts. He said that the sloped part is treated the same way that a wall would be treated. He said that the roof vents would provide enough ventilation for this situation. Since both contractors said the same thing, I guess I'll go with it.

 

[pmark]

I have a similar situation but my house is a cape. Two contractors told me to do dense packed cellulose in the slope parts so it seems to be a legit solution.

 

[Arcades]

1000sqft, I imagine this is a 1 story? Ice dams mainly happen because of snow melt refreezing. Reduce the snow, reduce the refreeze. You could probably do something like this

heated cable

 

[Blain]

Roof vents let hot air out, but need somewhere that cool air enters the attic.
If you don't add soffit vents, add some good gable vents.
Gable vents aren't as functional as soffit vents, but they'd help.

 

[TheSlamma]

1000sqft, I imagine this is a 1 story? Ice dams mainly happen because of snow melt refreezing. Reduce the snow, reduce the refreeze. You could probably do something like this

I mentioned the heat tape, but good call about the roof rake, especially with the wheels so you don't scrape the granules off the shingles.

 

[RU482]

cellulose sucks. so dirty/dusty. I don't think it would fare well in a a 4in cavity space. go spray foam if you can afford it

 

[Greenman]

cellulose sucks. so dirty/dusty. I don't think it would fare well in a a 4in cavity space. go spray foam if you can afford it

Getting foam down that cavity without blowing the interior plaster off will be a bit of a trick. I'd use dense pack cellulose.

 

[Vdubchaos]

Looks like you were already up there to take the pictures.

:biggrin:

Buy some insulation and stuff it in. What's the big deal?

Then, if you want, add the vent. I would either connect it to the closes/existing electrical cable or run the cable myself to the box and just have the electrician come in and do that part.

Sounds pretty easy to me.

Also, I have a feeling you are wasting your time anyways. Houses that old might not even have insulation in the walls (happen to know if yours does/doesn't). if it doesn't I wouldn't even bother with ANY of this.

I'm curious, how much does the insulation guy want for this work?

 

[richardycc]

find out if your state has any energy audit program that will pay for insulation, etc.
my state will pay up to $2000 worth of changes and material for any recommendations from the free energy audit.

a quick Google search found this: http://www.nysenergyaudits.com/

 

[cabri]

I had insulation blown into the walls of a 15 years old house about 5 years ago; about 300 linear feet of wall. The contractor was charging $4/ft. done in one day with all the prep.
They came back a second day for final cleanup and hole patching.

Between Federal Energy Credit/ State rebate and city rebate I paid $150 out of my pocket

 

[DrPizza]

find out if your state has any energy audit program that will pay for insulation, etc.
my state will pay up to $2000 worth of changes and material for any recommendations from the free energy audit.

a quick Google search found this: http://www.nysenergyaudits.com/

I nearly had an orgasm when I read your post. Darn it! It's NYC and NJ area; not all of New York State. My house would fail any energy audit; like the OP, about 2" of insulation in the ceilings. Getting ready to redo it, but having the state pay for it would be awesome. $2000 is a lot of insulation.

 

[cabri]

I nearly had an orgasm when I read your post. Darn it! It's NYC and NJ area; not all of New York State. My house would fail any energy audit; like the OP, about 2" of insulation in the ceilings. Getting ready to redo it, but having the state pay for it would be awesome. $2000 is a lot of insulation.

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[Murdoc]

Also, I have a feeling you are wasting your time anyways. Houses that old might not even have insulation in the walls (happen to know if yours does/doesn't). if it doesn't I wouldn't even bother with ANY of this.

I'm curious, how much does the insulation guy want for this work?

When the previous owner of the house had it vinyl sided, they put foam insulation board underneath, so I should be fine with the walls.

Cost to insulate just the cavities (slopes) - $380 for dense pack cellulose, $980 for closed cell foam.

$600 to blow 12" of cellulose on the rest of the attic.

I just recently had two other insulation contractors look at the attic. They both recommended spray foaming both the slopes, and the attic floor. They haven't sent me the estimate yet. They say they've been extremely busy this year.

 

[Fanatical Meat]

Looks like you were already up there to take the pictures.

:biggrin:

Buy some insulation and stuff it in. What's the big deal?

Then, if you want, add the vent. I would either connect it to the closes/existing electrical cable or run the cable myself to the box and just have the electrician come in and do that part.

Sounds pretty easy to me.

Also, I have a feeling you are wasting your time anyways. Houses that old might not even have insulation in the walls (happen to know if yours does/doesn't). if it doesn't I wouldn't even bother with ANY of this.

I'm curious, how much does the insulation guy want for this work?

From experience I can say attic insulation with none in the walls is still a huge help. Our house was built in 1959, we had 3 inches of 1970 type fiberglass insulation. I had 12 inches of cellulose added. That alone cut our oil use down by close to 40 gallons a month. The next year I had the walls done that saved about 10 gallons a month. After having the walls insulated we moved the night temperature up 3 degrees so the house was warmer and we used less oil.