Conventional vs. log home: how to decide which to build

Q. I would like to build a log house in northern California. Are modular log houses best? Are log houses better than conventional houses where the insulation R-factor is concerned? Where can I find some good log-house companies? Are conventional houses easier and cheaper to build than log houses?

E. V. Ruth A. More than likely only modular log houses are available from the manufacturers--probably in 2-foot increments, the same as dimentional lumber.

Both log houses and conventional buildings may need additional insulation against heat in the summer and cold in winter. It may be a tossup as to which is naturally better insulated, conventional housing or a log house.

The structures themselves--the type, thickness, and location of insulation in the walls, ceiling, and floor--tell the effective insulation story.

Check the Yellow Pages in your telephone directory under a title, such as ''log cabins, homes, and buildings,'' for a list of manufacturers.

Here are three log cabinmakers in the western part of the country:

* Arizona Real Log Homes, 532 Onyx Drive, Prescott, Ariz. 86312. (602) 445- 5437.

* National Log Construction Company of Montana, PO Box 68, Thompson Falls, Mont. 59873. (406) 827-3521.

* Building Logs Inc., PO Box 300, Gunnison, Colo. 81230. (303) 641-1844.

Which is easier and cheaper to build, a log cabin or a conventional house? That's a little like comparing apples to oranges. Each has its own rightful place on the dining table or in the building industry.

I'd let my own aesthetic tastes, as well as the environment where the building is to be placed, govern my choice of whether to build a house of log walls or a house of sawn-board walls. The wall costs are likely not all that significant, anyway.

For more information get in touch with the Department of Agriculture's Forest Service, PO Box 5130, Madison, Wis. 53705, and ask for the following:

''Building a Log House,'' No. 28, University of Alaska; ''Protecting Log Cabins, Rustic Work, and Unseasoned Wood From Injurious Insects in the Eastern US,'' Farmers Bulletin No. 2104; ''Making Log Cabins Endure,'' No. 982; ''House Foundation of Treated Wood After 30 Years' Service,'' research paper FPL-098.

''Forest Products Laboratory Natural Finish,'' research note FPL-046; ''Wood Finishing; Weathering of Wood,'' research note FPL-0135; and ''Wood Finishing: Water-Repellent Preservatives,'' research note FPL-0124.