Home Improvement : Increase Insulation to Cut Down Heat Loss
QUESTION: Our 2-year-old house is fairly energy efficient. However, we have two large return air ducts in the attic with about only one inch of insulation on them. I feel that I may be losing quite a bit of heat through them, but contractors don’t think so. I also think that air-conditioner ducts suffer similarly but in the opposite direction by warming the cold air instead of cooling the heated air. Am I right?
ANSWER: I agree with you. Contractors were using one inch of insulation on duct work before the 1973 oil embargo as standard practice. Since then, everyone has become conscious of the need to conserve energy. Attics that were insulated with three inches of fiberglass for an R-value of R-11 back then are now being insulated with six to nine inches of fiberglass for R-19 to R-30, or two to three times as much.
The more insulation on a duct, the less heat loss there will be in winter and heat gain (for air-conditioning ducts) in summer. However, because the law of diminishing returns applies to insulation effectiveness, there is a break-even point beyond which the added cost of the insulation exceeds the savings in fuel, so adding more may not be cost-effective.
There are so many variables involved--including degree days in your area, the efficiency of the heating system, the number of hours it operates per day at different temperatures, the velocity of the air moving through the ducts, and energy costs for heating the air through the system--you would need a computer to determine the optimum amount of insulation needed. And even then you might go wrong by leaving out some factor like interest rates or local labor costs.
As a rule of thumb, though, the Small Homes Council-Building Research Council at the University of Illinois recommends a minimum overwrap around a duct of three inches of insulation. If the duct is to be used for air-conditioning, it should have an outer covering with a vapor barrier to prevent condensation from wetting the insulation.
Try Vinegar to Clean Humidifier Sediment
Q: My hot-air furnace system is equipped with a power humidifier. The water in our area is hard and my system incorporates no water softener. The plastic basin and carousel of the humidifier must be cleaned regularly. The problem is a hard sediment forms on the basin and carousel and is extremely difficult to remove. Do you have any suggestions to make removing the sediment easier?
A: The hardened sediment that forms on the basin, carousel and flat assembly in your humidifier can be softened by soaking these parts in a solution of 50% white vinegar and warm water for about half an hour. The sediment can then be removed easily and the items cleaned. Rinse each component thoroughly and wipe it dry before putting the humidifier back together. If you don’t, the circulating air will pick up a vinegar odor for a while.
Dirt Basement Cause of Excess Moisture
Q: We had a new church built two years ago, and we still don’t have a concrete basement floor in it. The basement walls are always damp. Sometimes there are beads of water and mildew on them. There is also a real musty smell at times. I don’t think we have water coming in from the outside. I think we have a serious sweating problem. What do you think?
A: It sounds as if a lot of moisture is entering the basement from the dirt floor. If your church cannot afford to cover the dirt floor with a concrete slab, then it should at least cover the floor with 6-mil. polyethylene sheets.
Even when the dirt floor feels dry to the touch, a considerable amount of water still evaporates into the atmosphere of the basement because of the capillary rise of ground moisture.
According to the Small Homes Council at the University of Illinois, the soil under a 1,000-square-foot house can release as much as 18 gallons of water per day through evaporation.
Even with a concrete slab or vapor barrier covering the floor area, it may be necessary to use a dehumidifier to help control the amount of moisture.
