Q - I am planning to have an energy-efficient house built. Would "superinsulated" construction really lower my heating and air-conditioning costs and would it still look like a normal house? B. B.

A - "Superinsulation" really refers to very energy-efficient construction. There are many construction methods and designs of superinsulated houses. Other than thicker walls which are only noticeable at the window openings, a superinsulated house may look like any other house on the street.Heating and cooling costs for a superinsulated house are usually only a fraction of those for an ordinary house. Superinsulated houses in some cold northern climates can be heated for less than $100 a year. In hot climates, summertime air-conditioning costs are extremely low too.

Although superinsulated houses are highly insulated, airtightness is also a major factor in their low utility costs. Many of these houses use a continuous plastic film air/vapor barrier inside the walls. Another design uses the drywall itself as the airtight barrier. This is called "ADA".

In addition to the energy savings, airtight construction makes these houses very quiet and provides excellent indoor air quality. Since a fresh-air vent system is needed, you have better control over the air quality and its cleanliness. This is particularly beneficial if you have allergies.

There are several common construction methods for superinsulated houses. One of the early methods uses double studded walls. There are two insulated walls with more insulation in between them. This method makes installing a continuous airtight film barrier easier.

Another method uses insulated 2x6-studded walls with exterior foam insulation board over that. Although 2x6 studs cost more than 2x4's, you can usually put them on 24-inch centers. Therefore, you need fewer.

The increased cost of building an airtight superinsulated house varies depending on your plans and the experience of your builder with these construction methods.

Based on your climate and local utility rates, your builder should do a financial payback analysis of the energy savings versus the construction costs. Superinsulation does not provide the best payback for all designs of houses in all climates. However, you should also consider the other benefits and increased resale value of a house with low utility costs.

You can write to me for UTILITY BILLS UPDATE No. 319 showing diagrams of several superinsulated wall construction methods, diagrams of the ADA airtight method, and a list of suppliers of some of the special materials used. Write to James Dulley, The Deseret News, 6906 Royal Green Dr., Cincinnati, Ohio 45244. Please include $1.00 and a self-addressed envelope.

Q - I am having a new high-efficiency gas furnace installed in my home. My son wants to install my older gas furnace in his home, using bottled gas, LPG. Will it work for him? G. W.

A - A gas furnace burns LPG with no problem, but it needs to be recalibrated or have the burner modified. Many of the newer furnaces carry different model numbers for the natural gas and the LPG models.

LPG is delivered to the furnace burner at a higher pressure than is natural gas. Since it is at a higher pressure, LPG uses a smaller orifice in the burner to provide the right amount and mixture of fuel and air. Your furnace contractor or technician should be able to make the necessary modifications to the furnace.