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VitoB 11-29-2012 07:34 PM

Attic Insulation Question (PICS INSIDE)
Hi everyone,

I am glad to have finally joined this forum, I have visited many times.

I have a 2 storey home built in 1973, it has a 4 sided mansard roof. I live in Montreal, Canada where the winters are very cold.

Here is the amount of insulation I currently have in the attic:

Underneath the blown in fiberglass, I have fiberglass batts between the rafters.

The home always feels cold in the winter, although I also have many of the original windows which have not been changed yet.

Do you think I have enough insulation in the attic, or should I add some blown in cellulose on top of it?

Thanks everyone.


joecaption 11-29-2012 08:20 PM

Anyone making a guess would have to know what the R value of the fiberglass you have now is and the depth of the blow in is.

Did anyone air seal that attic before blowing in the insulation?

Your most likly loosing most of your heat out those old windows and leaking door seals.

Any insulation under the house?

jklingel 11-30-2012 12:21 AM

as joe said, kill air movement first. then, blow in as much cellulose as your sheet rock (??? whatever's on the lid) can hold.

VitoB 11-30-2012 07:23 AM

When air sealing the attic, I need to caulk or spray foam around the electrical boxes in the ceiling and the plumbing vent right?

Are there any other places in the attic to air seal? I do not have any recessed lights, only regular light fixtures in the bedrooms and bathrooms.

joecaption 11-30-2012 08:22 AM

And anyplace wiring was run though the top plates both in the attic and in the basement or crawl space.

VitoB 11-30-2012 10:16 PM

I did a lot of rewiring in my home, it had aluminum wiring. I replaced it all with copper. I will seal off where the wires enter the attic from the top plates as you suggested.

Gary in WA 11-30-2012 11:40 PM

The mansard:

Incense smoke test, check the carpet:

Air sealing:

New energy levels:

You could also install some housewrap on top the existing f.g. to stop any convective looping (in older low-density f.g.= if the ceiling drywall is close to its load limits (as JK said already):


VitoB 12-02-2012 06:35 PM

Thanks everyone for all the useful information and advice.

I went up in the attic today and I sprayed some foam around the electrical boxes.

I have about 6 inches of pink fiberglass in between the rafters. On top of that I have the blow in pink fiberglass, however it's very uneven. Some areas have almost 1 foot, and certain areas only have maybe 3-4 inches.

When you blow in the cellulose, does it create an even air barrier everywhere in the attic? I would imagine that's the biggest advantage since the smaller pieces will fill in all the voids and block the air.

Should I go for it and add some cellulose?

joecaption 12-02-2012 06:45 PM

Just take a hard rake and flip it over and level it out.

Gary in WA 12-02-2012 08:14 PM

Then add the cellulose if the ceiling board can take it. Stop those convective loops;


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