Expert: Richard Taylor, AIA - 1/21/2004

Question
I am adding a 16x16 room to my home in the Detroit area of Michigan.  It will have a vaulted ceiling and a crawl space under the floor so the floor will be on the same level as the rest of the house.  The floor will be carpeted, and there will be four insulated windows in the room.  We will be extending two forced air heating ducts under the floor into the room.

What level of insulation do you recommend for the walls, ceiling, and floor?

Thanks.

Answer
Jim:

Thanks for your question!

Insulation standards are governed by building code and vary from location to location.  You'll have to meet local codes which may include the Mechanical Energy Code, which takes windows and heating systems into account.

Best bet is to contact your local building department or a local insulation contractor.  Your local building supply house may also be able to help you out.

Generally, you'll probably be expected to put at least R-19 in the floor (if it's not a heated crawl space); R-15 in the walls; and R-38 in the roof.  For the vaulted ceiling, be sure you allow the proper air space over the insulation and vent both the eaves and the ridge.  All the major insulation companies manufacture special ceiling batts for cathedral ceilings.

If you do heat the crawl space, you'll need to insulation the foundation walls, probably to about R-10 or so.  An unheated crawl must be vented; a heated crawl does not.

Finally, improperly installed insulation and vapor barriers are a major cause of building material failure, water problems, and mold growth.  Be sure you install the materials correctly!

Hope this helps!

Richard Taylor, AIA
Richard Taylor Architects, LLC
www.rtaylorarchitects.com