Q - Is it possible to design our new home to use passive solar heating for almost all of the heat in the winter? Would that type of home look strange and how much window area would we need? D. D.

A - It is possible to design a house so that passive solar heat provides the majority of the heating load. Using new types of high-efficiency window glass is important and makes solar heating even more feasible now.These types of houses are very attractive, and can be built at costs comparable to standard houses. With the large window areas, they provide a very open feel, with the indoor living areas integrating well with the outdoors.

In all but the milder climates, you generally need a small amount of backup heat during extremely cold spells from December through February. In the long run, it is often less expensive to use some back-up heat instead of investing the additional construction money to attain 100-percent solar heating year-round.

A target solar contribution of about 80 percent of the annual heating load often is reasonable. You may want central air conditioning for the summer, which requires the expense of the ductwork anyway.

Common heat storage locations in these houses is in the attic and the lower level so it doesn't interfere with the view of the outdoors. By having the heat above and below the living area, this "heat envelope" maintains more comfortable living-area temperatures.

Since you must build an extremely energy-efficient house to utilize solar heating effectively, the total heating requirement is low. With a large active family, there may be enough heat generated by them to adequately supplement the solar heat during the cold months.

Just using electrical convenience appliances, like hair dryers, toasters, lights, etc., can add substantial heat. And you get the heat when it's needed most - when people are in the house.

The amount of required window area is usually expressed as a percentage of the floor area of your home. For a very energy-efficient home, you generally need window area equal to 25 to 50 percent of the floor area. Very mild climates may require less and the northern climates, like Grand Forks, ND, may still need some back-up heat with 50 percent window area.

You can write to me for UTILITY BILLS UPDATE No. 340 showing exterior diagrams and floor plan layouts for four solar-heated houses, a list of manufacturers of high-efficiency window glass, and a chart of the required window area for houses in 25 cities throughout the U.S. Write to James Dulley, The Deseret News, 2654 Jessup Road, Cincinnati, Ohio 45239. Please include 75 cents (no checks, please) and a self-addressed envelope.

Q - The locks on our double-hung windows don't work well. Is it important to use the locks to make the weatherstripping seal properly? K. B.

A - Most newer windows are designed such that the locks hold the sashes together. This compresses the weatherstripping and provides a much tighter seal. Usually, the weight of the window itself is sufficient to seal against the bottom weatherstripping when it is closed.

On some older warped windows, the lock can actually push the sashes slightly apart. The best way to check it is to test the air leakage, locked and unlocked, on a windy day. Hold a lighted stick of incense up near the window and you'll see which way the air leakage is the greatest.