Very warm on top floor...

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Old 06-14-01, 10:01 AM
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Just wanted to say that I've learned a lot already by just reading all the posts similar to my situation. However, I do have a few questions for the "experts."

I recently moved into a three story townhouse which is 10 years old. There are three distinct temperature zones with the basement the coldest and the top floor the warmest. (I'm expecting rain on the middle floor any day now...) The top floor has vaulted ceilings with a skylight at the top of the steps.

We've been having very warm weather recently and the top floor is close to being a greenhouse... After reading some very helpful posts, the first thing I think I need to do is add insulation on the floor of the attic. (The attic only covers the two top floor bathrooms.) There currently is no insulation. My first question is should I also consider adding a fan in the attic to vent the hot air or will adding R-49 insulation do the trick?

My next question is about the vaulted ceiling / skylight. The heat from the sun onto the top of the steps is a problem. Any suggestions?

Thanks in advance,
RJ
 
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Old 06-17-01, 04:46 AM
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Disclaimer: I'm no expert - I'm just offering my opinion after reading for several days about insulation.

First, it seems odd that if your house is only 10 years old that there is no insulation. You make mention of cathedral cielings, and those must be on the top floor of your 3-level house. Usually there is insulation behind the drywall in the cielings. Your attic sounds a little strange (to me), but I wonder if the cathedral cielings are contiguous with the "cieling" of the attic. If so, then there ought to be insulation in the cielings all the way down. If so, then you already have a layer of insulation protecting the attic, although it's not very much (not over R-20). I don't know the effect of placing insulation on the floor if there is insulation in the cieling, but I have seen elsewhere that you ought not to insulate rafters and knee walls both (insulate one or the other) and this seems somewhat like the same situation. But if there's no insulation in the top of the attic, then adding insulation on the floor would be a good thing but I don't know how much difference it would make given that it's only above your bathrooms.

An attic fan seems like it wouldn't make much difference for the same reason; it would help your bathrooms, but the rest of the house still lacks insulation. I have heard mixed stories on attic fans in general. My belief (after reading DOE data) is that attic fans do cool the attic, but in doing so they suck cool air out of the rest of the house to do so and therefore waste "conditioned air", negating any benefits. It seems that if you have a good soffit/roof vent combo that is appropriately sized then this will work in a passive fashion quite well. I suppose a low-flow thermostatically controlled fan would be a good compromise if one really felt it necessary.

So, IMHO, there are still a few things you can do:

1)Apply a reflective roof coating on the outside. These generally are white paint-on coatings that make the most difference when the attic is not well insulated.

2)Find out what insulation you do have in your cathedral cielings, and think about extending the rafters with wood strips so that you could fit a higher level of insulation behind the drywall. Of course, with drywall, you run into a weight limitation but I bet there's a way around that by securing the insulation prior to contact with the drywall.

3)Apply a low-E paint like Radiance(www.radiance.com). Their claim is that it acts as a radiant barrier in the summer and winter. I have no problem seeing how it would work to keep heat in, but the claim of keeping heat out seems a little odd as there's no open area for the reflective properties of the paint to work (and I'm under the impression that you need at least a little bit of space for it to work, since radiant heat travels through space).

4)As far as your skylight, there are a number of window coatings/films that will allow light through but cut down on the amount of heat making it through which should be the simplest thing to do out of all the suggestions.

Again, I'm no expert, and I don't know if I correctly understood the way your house is constructed, but I hope that helps!

Nick Browning
 
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