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Pawige 08-31-2009 12:43 PM

How to insulate this attic?
Hello all! I'm trying to do a pretty big insulation project and need some advice on what would be the best approach. This is an older house and it leaks a lot of heat through the roof and the walls of the second floor. There is already a layer of blown-in insulation in the attic and I'm not sure what the best approach is for improving insulation there. Also, there are a lot of tight, sloped walls which are insulated very poorly and I need to figure out how to fill those. Can it be blown in from the attic? Can I to blow it in through holes in the wall? Or would installing batting be best?

Here's a picture of part of the attic:
The area I'm looking to get insulation into is down and to the left in the picture, it's probably a gap of about 4 inches or so in most places. A lot of the gaps along the edge are covered in the blown-in stuff already, but about 50% of them are easy to access.

If I've left out anything important, let me know and I'll post any other info you might need.

Thanks a lot!

RDS 08-31-2009 01:03 PM

Not my area of expertise, but by the "gaps along the edge" do you mean the spaces between the ends of the rafters? If so, do you have soffit vents there? Because if so, they need to be kept clear of insulation to operate properly. Apologies if I'm misunderstanding you.

Pawige 08-31-2009 01:39 PM

There are soffit vents, I hadn't thought of the difficulty there, actually. But the problem is that the slope of the roof cuts into the room, like so:

So the wall is about 40% slope and 60% vertical.

Here's a look at the outside:
I outlined the vents here. The real problem is that a lot of heat is lost through those slopes and the walls. Just not sure what exactly can be done about it.

Paragon 08-31-2009 04:01 PM


First of all one thing I see wrong with your attic space is that it is underventilated. I would get more vents in those soffits so that you get proper ventilation in the attic. Also when you add those soffit vents install baffles so that you get proper air flow from the soffits all the way to the ridge area vents. You can vent the roof out the top a couple different ways with turtle back or slant back vents. You can also install ridge venting however with existing shingles there will probably be a color mismatch unless the shingles are REALLY new, lol. Ventilation is extremely imprtant and in your case I may not be seeing some turbine vents however your venting issue should be examined either by you or a reliable and credible contractor.

Now as far as insulation how deep is the insulation that is in the attic right now? In our part of the US we use an r value of 50 now for proper insulation and a visit to this insulation chart may help you determine the proper level of insulation for your geographic area and how to acheive it.

Also You mentioned that you are experiencing heat loss on the second level if I am correct. I looked at the pictures of the attic space and it looks like there is at least 10 or so inches of insulation there now which tells me you have some insulation in the attic. Howeve, when I look at the pictures of the drywallled rooms that you kindly provided us with I wonder to myself what is on the other side of those walls. The portions of vertical wallthat comes up 4' or so from my experience usually has a crawl space or storage space that is accessed by some kind of a small door leading into a space that is triangular shaped. So my question now is what is there on the other side of these sheetrocked walls that we see in the pictures? Are these walls insulated at all? I would say that if you are experiecing extreme heat loss that this might be a place to start looking and then go from there.

Hope that his helps and good luck.

Gary in WA 08-31-2009 08:44 PM

It looks like you have ridge exhaust vents, which is great. As mentioned by Paragon, the soffit (supply) vents are lacking. Look under the insulation for a vapor barrier as it changes the ratio of venting required:,M1
Is that a snow cover or ? on the washing machine vent pipe?

The gable vent is counter-productive, as per article.

Here is your house, the R values may be wrong:
I'd make sure the bath fan termination (in the picture) is caulked behind it to the siding (any wind blown rain hits it directly from the shed roof).
Any other questions, just ask!
Be safe, G

Pawige 08-31-2009 09:38 PM

The house was built in 1910, there's no space for crawlspaces behind the walls (which are lath and plaster) as the roof ends where the wall goes vertical. While replacing all the second-story windows we saw no signs of insulation at all.

The roof was recently redone and we had ridge vents installed then. Taking the gable vent out would be good in more than one way I guess, as that would hopefully keep the bats out too... And the black thing is a snow cover, I'm in northwestern Minnesota.

The insulation in the attic itself is about 4 inches thick on average, though depending on the spot it could be as little as 3 or a much as 12, it's very unevenly spread.

Thanks for all the advice so far!

Gary in WA 09-01-2009 11:18 AM

I would remove the soffit plywood, install the 8' cellulose insulation tube (only) up the slope ceiling, install some baffles taped together to reach 18" past the attic/ceiling joint-down to the soffit vent, blowing in cellulose as you fill the slope, pulling the insulation tube out while letting the insulation lift the baffle up to the roof deck underside surface, blow-in insulation to the now accessible walls, and adding continuous venting near the fascia board (as per article) to the new soffit material prior to the installation. Install blow-in from the attic crawl to the attic to get required R-factor. Don't install close to any B-vents (exhaust) for gas appliances, or over any older can lights. Use oil based paint (moisture retarder) on the walls and ceiling in case there is no vapor barrier or retarder on the existing insulation. Seal at electrical outlets so insulation dust doesn't enter room. Ask on our electrical forum if you have knob and tube--- for any heating-up due to insulating. The box stores sell the insulation, let you use the blower for free. Moving on to the basement.......

Be safe, G

99miles 09-01-2009 02:21 PM

Hi Pawige-
This is slightly off topic, however your space looks very much like the shape of my attic, which I am planning to convert to a master suite before too long. I would LOVE to see more photos of the space that has been converted to get ideas if you have any and would be willing to share.

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