Heat Transference Question

[gaming_mouse]

So this is a science question with a practical application.

My house, an older construction, gets very cold in the summer and very hot in the winter, and so either my gas bill (heating) or electric bill (air conditioning) is high.

In the winter, it helps alot to put the shrinking clear plastic insulation over the windows -- I believe because it slows the exchange of cold and hot air from outside and inside the house.

My question is: Would that same insulation also help in the summer (by keeping the cooled AC air inside)? Or would it, combined with the sunlight coming in, create a greenhouse effect that would actually make the air conditioner less effective?

What says Mr. Wizard?

[madnak]

I'm not an expert, but there are three types of heat transfer - conduction, convection, and radiation. The plastic may have some effectiveness for conductive and convective transfer, but not so much for radiative transfer (ie sunlight). So in the summer it would be less effective.

[arahant]

I assume you meant hot in the summer, cold in winter...

There's a lot of subpoints I could write here...short answer is it will help in both summer and winter.

In the winter, much of the cooling is from temperature differential, as it is is usually like a 40+ degree (F) difference between your house and outdoors. Unless you live in phoenix, it's almost always less than this in the summer, and the heating comes from the greenhouse effect.

But the plastic should actually reduce this, by blocking some of the incoming sunlight.

[Siegmund]

As others have said, the plastic helps, not hurts, with the greenhouse effect in summer too. Once the photons come through the glass they are inside your house and about to make it hotter. The more of those you can confine near the window, the more of them are going to make their way back out.

The only downside to the plastic that comes to mind - aside from appearance - is that in summer you might be opening windows at night to help the house cool down, and the plastic would get in the way of that.