Home>Discussions>INSULATION & HVAC>Replace Fiberglass Insulation with Foam
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canuk
Re: Replace Fiberglass Insulation with Foam
Earnie wrote:

Since the existing batts are kraft faced, would there be an issue with re-installing the old kraft batts on top of the foam? Or should non-kraft batts be used?

Sounds like the foam will be applied toward the room side and then the bats overlapped toward the roof side ? If this is the case I would recommend removing the kraft face from the existing insulation before re-installing. The reason being any humidity that will accumulate in the attic space with infiltrate the bat insulation and the kraft paper will hold that moisture within it. The unfaced will allow bat insulation to breath and not let the moisture to accumulate.

Quote:

If new non-kraft batts are necessary, would blown-in insulation be better on top of the foam?

I don't believe this is a good way of doing it. The foam requires a stable base to adhere to and the bat wouldn't necessarily provide that. Plus when the foam expands it will compress the bat insulation reducing it's performance and negating any intended benefit.

keith3267
Re: Replace Fiberglass Insulation with Foam

As the owner of a log house, I have very strong misgivings about foam against wood. When my house was built, it was a common practice to use foam between the logs. Unfortunately, the foam often used was open cell foam, which absorbs and holds moisture against wood. Wet wood rots.

If your fiberglass insulation was installed with care, and it usually isn't, then warm rising air would have a difficult time escaping through the gaps in the tongue and groove ceiling boards. As long as there is outside air flow over the top of the insulation, it will remain dry and effective.

If the wings of the kraft faced insulation was stapled to the inside face of the rafters, as it often is, then gaps form along the edge that allow air to escape. It is better if the wings are stapled to the bottom edge of the rafters and they overlap each other a little, if this were done, then I see no benefit to going with foam.

If the wings are stapled to the face of the rafters as is common practice, then I recommend looking in a chinking product used for log homes. It will change the aesthetics of the ceiling, but that could be a positive, it just depends on your taste. They are available in colors so you may get a good match that would hardly be visible or you could go with white and have very visible lines.

The chinking would prevent any air infiltration into the attic so the fiberglass would do its job.

If you are considering the foam because you think it will save a lot of energy and therefore money, I think you may be disappointed.

Earnie
Re: Replace Fiberglass Insulation with Foam

Kraft paper wings were stapled to the "inside" of the rafters, not the flat edge. I have a picture showing the installed batts before the T&G ceiling was installed.

So much for a quality insulation installation or quality building inspection.

The intention of the closed cell foam is to seal the air gaps in the T&G boards. Probably only one inch of foam. Then, as Canuk has suggested, possibly removing the kraft paper and re-installing the fiberglass batts on top of the foam. The foam is the air/moisture barrier and the batts are the insulation.

This is a log house. My quess is, the T&G boards were not allowed to climitize before installation. The boards have separated to the extent that I can see the kraft paper between a few of the gaps. That can't be good.

Chinking between the gaps might work, but I suspect it wouldn't look so good. Chinking looks great on the logs but having a chink line every six inches might be a bit much even it the color closely matched.

JLMCDANIEL
Re: Replace Fiberglass Insulation with Foam

1]It's open cell foam, we have already recommended against open cell foam. From their web site-
SEALECTIONTM 500 spray foam insulation is applied by Approved Applicators, which provides a truly effective method to construct energy efficient homes and buildings. SEALECTIONTM 500 is a semi-rigid thermo-set polyurethane foam (see Product Specifications), which is a cellular plastic composed of millions of microscopic cells of which most are open.
2]It expands 120 times it's sprayed on volume which wouldn't leave room to add the fiberglass.
Jack

Earnie
Re: Replace Fiberglass Insulation with Foam

Good catch Jim. Sorry for the wrong link. That was the first one Google provided.

Here is the main link: http://www.demilecusa.com/

HeatLok is their rigid foam: http://www.heatloksoy.com/main.php?p=en-about-heatlok

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