Insulating the Roof and Installing Mold-Resistant Drywall

The roof of the new addition is being insulated – in an environmentally conscious way – to retain the heat from the radiant heating system. Moisture- and mold-resistant drywall is being used throughout the addition.

Clip Summary

The roof of the new addition is being insulated to retain all the heat generated from the radiant heating system. Paul Johnson of Alpine Insulators reviews the installation process. Fire-retardant netting is stapled in place to hold dense-packed cellulose in place. Cellulose is a great thermal insulator and sound attenuator. In the interior partition wall where the bathroom will be located, cellulose will be installed directly against the drywall.

Bill Hulstrunk of National Fiber discusses cellulose insulation, which has been around since about 1920 and used extensively since 1970 in both new and existing construction. Borates are added to make the cellulose fire retardant, and mold and insect resistant. Because of the added borates, a propane torch can be put to the cellulose without igniting it. These borates are naturally occurring and the cellulose is made of 83 percent recycled content, making this type of insulation an environmentally conscious, green choice. The cellulose in this house is being used in an unvented application. Because the material is packed very tightly, it reduces the chance that warm, moist air will penetrate the cavity and create mold growth.

Georgia Pacific DensArmor drywall is being used throughout the addition. The face of this drywall is made of fiberglass so there is no danger of hosting any sort of mold growth. Attaching the drywall to a foam-and-concrete structure posed a bit of a challenge. To address this, steel J-beads were installed horizontally as nailers for the drywall screws.
And inside the house, we've been busy insulating that new roof to keep all the heat in. Howard chose to use a natural product as well.

Well the first step is installing some netting.
This is a cross- linked polypropylene netting.

The most important feature of this is that it's breathable, so that when we blow in at high pressure the cellulose, the air can come out and escape so it can be packed very densely.

Ok this, this is a fire retardant netting. It's stapled up in a very tight manner so that we can get a maximum amount of cellulose in here.

In the truck we have the insulation sheet. There we empty the bales of cellulose where they are shredded up even further, and they are pumped at a high pressure through these hoses and into the cavities.

Here where we have a roof assembly with 2 by 12 rafters, where we had scrapping and we've netted over it, it would cost about $2.25 a square foot. Cellulose is not just a great thermal insulator, it's a great sound attenuator.

In this interior partition wall of the bathroom, we will be installing cellulose, directly against the drywall, prevent sounds from traveling from the bathroom to the hallway.

Cellulose insulation has been around since 1920, and has been used extensively since 1970, both in new and existing construction.

It's the borates that are added to the material that really give it the, the enhanced fire-retardant, mold inhibitors and repellent for insects .

The key thing to know about Newell is that this isn't just ground up newspaper . This has borates added that impart significant fire protection to the material. In the field we can do a test where we take a a propane torch, and put a penny on here, and can melt the penny without the heat actually going through and you know, heating up your hand or affecting your hand.

After that cools you then scrape away, you know, an eighth to a quarter inch of material, and there's fresh material underneath that.

Not only do Borates offer significant fire resistance but they are also mold inhibitors and resist insects but the best thing about boards are naturally occurring, and that along with a material that's made from 83% recycled content really offers environmentally green, green product.

In this house, we're using the cellulose in the unvented application. So first of all we're going to maximize the potential or the depth of thickness of the insulation, by fully filling that cavity.

And then because we're dense packing or packing it in very tightly, we will eliminate the potential for warm moist air to permeate through that cavity and potentially condense, and that offers the both the performance of the insulation and the protective aspects of the material. Now, we're using Georgia Pacific DensArmor drywall throughout the house.

And you know, one of the great advantages of this kind of innovation in dry wall is that, because the mat basing is not made out of an organic paper, it's made out of a fiberglass type of paste, you don't have any danger of hosting any sort of mold growth.

And that's a really important thing nowadays in most house construction.

Here we also have the added complexity, if you will, of having to install it onto this concrete and foam structure.

So there were these steel J-beads that were inserted horizontally, and they provide nailer, if you will, a place for the drywall screws to fasten to, and that's how they all were installed.