and (hopefully!) insulation. Floor insulation was not standard when homes with elevated wood floors were built fifty or more years ago. So, if you see any fiberglass insulation batts tucked up between the floor joists, they were likely a recent improvement. The R-rating of the insulation will be marked on the paper sleeve of the insulation, and is usually around R-20. The batts should be mechanically held in place by bowed strips of metal between the joists and possibly netting across the bottom of the joists. Be sure to sweep your flashlight beam across the entire area visible from the opening, looking for any insulation that has fallen down or been pulled down by critters that have gotten under the home.

WALLS - Checking for wall insulation is a little more complicated. Because any insulation is sealed between the exterior and interior wall coverings, you will have to remove a cover plate at an electric outlet/receptacle in one or more locations at an exterior wall and peek into the small gap in the wall between the receptacle box and the wallboard to look for insulation. But, very important: before you remove any cover plates or do any probing next to the receptacle box, turn off all power to the home at the main breaker.

   It helps to shine a flashlight in the gap around the receptacle box and you may be able to get a screwdriver in the opening to expand it just a little. If you don’t find evidence of insulation at the first box or there isn’t enough opening to get a good look, move on to a second or third box to be sure.

   Walls are the least likely location to find insulation in an old house, and also the most difficult for retrofitting insulation if there is none. Unless you are planning on removing and replacing all the wallboard on the exterior walls as

part of a remodeling, a hole has to be drilled in each in stud cavity above and below any firestops before insulation is blown or foamed into the cavity, Finally, each wall opening must be repaired. It’s a lot of work.

ATTIC - Most older homes have attic insulation and, often, there are two layers. Beneath a top layer of new blown or batt insulation is usually an older layer of original insulation that has become compressed over the years and has minimal R-value. Using a sturdy ladder to get to the attic hatch opening, remove the cover panel, and stick your head up in the attic with flashlight in hand. It is not necessary to climb into the attic. You may find blown fiberglass or cellulose, older rock wool batts, or fiberglass batts. The thicker, the better. But also look for any areas of insulation that have been compressed by workmen crawling around the attic. Newer insulation installations will have a rating card near the attic opening detailing the type of material and R-value. Also, if it is blown insulation, you will also see measurement sticks at several locations (like in the photo at the top of the page) to confirm the thickness of the insulation blanket.

WINDOWS - The insulating value of double-pane windows and sliding glass doors is typically between R-2 and R-4; not a lot, but every bit helps. To verify that windows are double-pane, hold a flashlight up against the glass at a 45º angle. The beam of light will illuminate each pane.

   If the glass panes are cloudy, it means that the inert gas between the panes has escaped, reducing the insulation value of the window. Also, because the fogging is on the inside of the glass and not cleanable, it reduces the light transmission and appearance of the window.

R-RATING - The ability of a material to resist the passage of heat through it is measured by its R-value. The higher the number, the better the insulating ability. Fiberglass batts in a 4-inch stud wall are R-11, and R-19 in a 6-inch stud wall cavity. Both fiberglass and cellulose insulation are rated at about R-3.5 per inch thickness. Here’s a chart for estimating the R-values of various materials, based on their thickness:

The new spray foam insulations, like in the photo below, are rated at about R-6.5 per inch in closed cell version and R-3.5 for open cell, and are typically applied to the underside of the roof sheathing.

While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here.
©2015 - McGarry and Madsen Inspection.


Fiberglass Batt Insulation

Blown Fiberglass Insulation

Cellulose Insulation

Chart - InterNACHI

How to Look

at a House

A blog with answers
to your questions about

Search This Blog

Welcome to our blog!
We want you to be an informed homebuyer, and each blog post is a question that we have answered for our friends and customers over the years. Hope they help you make a good choice for your next home.

Click Below to Link
to Collections of
Blog Posts by Subject

Search This Blog