DIY Sarah

Craft, Decor, Art, Garden, and Dessert

Insulation Cellulose vs Foam, Vented vs. Closed roof

You’ve been hearing me talk insulation for a while now.  I figure it’s high time I explain our insulation choices and struggles.

Let’s start with the walls.  In general, there are 2 modern ways to insulate: foam and cellulose.

Cellulose is a recycled paper product that coated with boric acid to prevent it from burning.  You can read all about it on wikipedia HERE.

Foam is an expanding foam material similar to the spray foam product “Great Stuff.”

For the open walls, there are a few options. For the cellulose, there is a way to spray it on wet kind of like paper mache. Stefan’s brother has experience with this method but we couldn’t find a contractor that used wet-spray cellulouse. For the most part, the did net and blow where they staple up netting and fill the open voids with the cellulous. The other option is a foam application.

AFter spraying in the foam, they use another tool to cut off the excess flush with the beams.

IMG_1892.JPG

Generally, the foam is more expensive. We found a contractor that we really like that is itching for the bigger job of insulating the whole house so the foam ended up being quite a bit cheaper. We will re-evaluate what we want to do for the rest of the house but the open areas are foamed.

When looking at insulating the attic, there are 2 schools of thought. First there is the traditional way to insulate. The traditional way involves maintaining airflow from the soffits up to the roof vent of the attic. The second says to foam it up and make the attic closed.

Vented Roof:


This image is from a Univeristy of Central Florida paper on vented roof systems.

This is an excellent pdf that explains the vented roof idea:
Crash Course in Roof Venting

 

Closed Roof:

This is a insulation specialist’s explanation of a closed roof system

Pros and cons:

THe closed roof system is more insulated. You can imagine that venting a roof makes it harder to heat. You can also imagine that having the roof closed up makes the house harder to cool in the summer. Normal operation has the hot air rising and exiting the roof vents. That’s a minor downside compared to the diminished life of the roof. Roofs like to breathe and to be the same temperature above and below the shingles. With the closed roof system, the underside of the roof is covered with foam instead of air.

Normally, we would stick to an open system without much hesitation. The difficulty is in the 3rd floor. The third floor is tucked up under the eaves of the roof. As you can see here:

IMG_1831.JPG

In order to have any insulation in the sloped portions of the 3rd floor bedrooms, we would need to go with a closed roof system.

Unless…we could do something tricky like:
IMG_1926.JPG IMG_1926.JPG&description=Insulation Cellulose vs Foam, Vented vs. Closed roof') ” alt=”” />

We used strips of 1.5″ pink foam to block out a ventilation chamber with 2 sheets of 1 7/8″ foil backed foam to build out the vent chamber and insulate the slope with R-24 insulation.

IMG_1945.JPG

THis is looking down the roof line. You can see the pink blocks and the two layers of R-12 foam.

We used the pink foam as blocking because of the number of nails in the roof. Using wood would have been next to impossible but the foam just popped right onto the nails and used the multitude of nails to hold itself in place. Brilliant!

One word of warning, this method isn’t cheap. with one sheet(2’x8′) of the pink foam and 4 sheets of the foil backed foam (4’x8′) we’re looking at $162 in foam alone for this little area. Add in the 5 cans of “Great Stuff” we used to seal everything up tight and we’re looking at about $200 for just 3 beam spaces. It will be more than $1000 and a lot of work to do this to the whole 3rd floor. It does require all the walls to come down to get access to the space. Needless to say we’re going to see how this does before we go whole-hog.

 

I hope this answers some questions you have about insulation.  Feel free to ask any questions in the comments and I’ll do my best to answer!

 

Sarah

 

Categories
reviews, Uncategorized