Cape style homes are classic and plentiful here in Northern New England, originating in the 1700’s as a practical, sturdy style home to withstand our weather. Unfortunately, they have those cold kneewall areas. These kneewalls are usually 2×4 construction with R-11 fiberglass and the cold air easily penetrates through there and on into the living space. Often, fiberglass is just hanging there by a staple or two after the mice raised havoc. The insulation that is on the flat ceiling behind the kneewall goes to the exterior wall plate and is below the proper vent. This leaves an area on top of the wall plate completely open to the outside air, which is why the area behind the kneewall is freezing cold. The R-11 fiberglass does not cut the mustard.
The solution to this problem is to block off the soffit area with ridged foam board while still leaving the proper vents in place, so that the outside air will go into the attic and not the house. Then, spray foam from the top of the exterior wall plate up to the proper vent, and continue with the spray foam all the way up to the top of the kneewall, to achieve R-49. The exterior gable end sides also need to be spray foamed to R-21.
This turns the space behind the kneewall into ‘conditional space’, which is now the same temperature as the rest of the upstairs living area. Problem #1 solved.
Next: the sloped ceiling above the kneewall is generally not insulated properly allowing cold air to penetrate thru the sloped ceiling into your living space. The solution is to dense-pack the sloped ceiling with cellulose – from up in the attic, filling the rafter cavity but not disturbing the proper vent. Problem #2 Solved.
“This process is not very expensive. The resulting warmth for your family also helps to keep your heating fuel in your tank”, says Russell Haney of Superior Spray Foam, Inc.
Case in point: A 6 year old cape that had been built for the homeowner just the way they wanted it, … except for the fact that the family had been freezing since they moved into the house. Recently, the owners were painting their daughter’s upstairs bedroom and the paint at the cold kneewall literally froze. It was a mess. A local contractor was called in to see what could be done. The above mentioned work scope helped these folks so that are now toasty warm with new paint on the walls.
Article contributed by Russell Haney, Owner of Superior Spray Foam Company, Inc., Bath, NH.