Home Insulation Projects

[mark.wolven]

Thinking about the coming Northern Virginia winter and life in a 40+ year old house.

The attic has old fiberglass insulation between the rafters. Some of it has settled in spots and it looks dried out and brittle if that makes sense. If that doesn't make sense - well, it still looks dried out and brittle to me....

Question 1: Would I get good bang for my buck by rolling out a new layer of R-13 over the old insulation - but at a 90 degree angle?

Question 2: Would a vapor barrier make sense in the attic? Would it be most effective under the insulation? Over the insulation? Or against the roof?

Question 3: I have a gas burning furnace in the basement. The furnace is in a room with the washer and dryer and in the winter, that room gets pretty warm. The vent pipe exiting the furnace gets plenty hot. Would insulating that pipe help keep the rest of the house warmer?

[ransley]

Check recomended R values for your area at

the attic is the cheapest place for most to add insulation, most heat loss rises. I would bet recommended is R35+. just go over what you have the vapor barrier should be flt against the ceiling. If you mean the venting pipes that circulate heated air it could help if the basement walls are insulated

[Joseph Meehan]

Any additional insulation is good.

Any vapor barrier should be on the warm side, that usually means next to the ceiling below, which would be under the existing insulation. Is there one under that insulation. If so leave it there. Don't choose insulation with an attached vapor barrier when you are adding insulation.

If you mean the exhaust pipe, then no do not insulate it. If you mean the ducts supplying warm air to the rest of the house, yes go ahead and add some insulation, but don't expect much. Since heat rises most of that heat that is now in your basement finds its way up to the living areas. Insulating the ducts would increase this some and reduce the temperature of the basement.

[Buck Turgidson]

I also have a similar house in Northern Virginia. My attic has a layer of tar paper laying on the ceiling drywall which serves as a vapor barrier. You might check to see if you have that.

If you don't have it, it needs to be on the heated side of the house, i.e. under the insulation.

[Calvin Henry-Cotnam]

Buck Turgidson (jc [e-mail]) said... [about vapor barrier]

It needs to be on the warm side of the dewpoint. If you were to move through the insulation from the warm side to the cold, the temperature in the insulation drops. At some point between the two sides, the temperature is cool enough that moisture in the warm air would condense (and form dew). That is the dewpoint.

Ideally, that means on the warm side of the insulation, which can be done if it were new construction or if you remove what is there.

However, if there is only about R13 there now and you were going to add another R22 to bring it up to R35, it may be possible to place a vapor barrier between the existing and new insulation. This would require some research looking into the temperature extremes in your area, though a good rule of thumb is that the vapor barrier should be no more than one third the way between the warm and cold (1/3 maximum of the total thickness between the warm side and the barrier - R13 of R35 exceeds this slightly, but R13 of R40 falls within 1/3).

[Bob F]

I thought the whole point of tar paper was that it passed water vapor but not water.

Bob

[mark.wolven]

There's existing insulation in the attic - above the ceiling, between the rafters. It's old. Probably original or close to it.

I believe that is does have an existing paper side to it.

So, it looks like a vapor barrier is out of the question, since I am not taking out the old stuff.

As for the basement, it is insulated and comfortable during the winter. The gas furnace is in a room with the laundry, and the main duct supplying hot air to the rest of the ducts. I am thinking about insulating this because the duct is so hot, you cannot even touch it. That to me, says heat is escaping.

[Bob F]

The "paper" is a vapor barrier probably.

That heat will be warming the area around that duct. Is it a heated area?

If the duct is so hot you can't touch it, you are either touching the exhaust duct, or your furnace is heating the air a lot hotter than any furnace I've experienced. Have you cleaned or replaced the air filter recently? It could be limiting the air flow.

Bob

[mark.wolven]

The is changed regularly, I have a thermostat that also counts the hours and has an indicator for when the filter should be changed, so, it's not the filter...

But the exhaust duct.... hmm... let me look at that.