Energy Efficiency - Home Insulation

Expert Insulation -

This educational article is brought to you by
Rochester Area Builders, Inc. with the support of Expert Insulation, Inc.





Whether you are building new or making improvements to your current home, it makes good sense to ensure that it is insulated properly. Stringent building codes assure that new construction is energy-efficient. However, in existing homes, this may not be the case.

Along this line, a little background may be in order. Until the 1930s and '40s, not much thought was given to home insulation. Energy was relatively cheap and conservation was not an issue. Even today, remodelers tearing down inside walls separating the interior from the exterior find horse hair, tarpaper, old newspapers or basically anything that people thought would help keep out the cold. In fact, there are still older homes that have no insulation within their exterior walls. It wasn’t until the 1950s that more attention was given to wall and ceiling insulation. And currently, although Minnesota Building Code has specifications for insulating new homes, there are no requirements for existing homes, even when they change hands in a real estate sale. Consequently, buyers of older homes should find out the extent to which their homes are insulated.

Insulation Creates a Barrier

The most basic function of insulation is to create a barrier between two different temperatures. As homeowners, we don't want to dilute warm air inside with cold, winter air outside, or vice versa during the summer months. The effectiveness of insulation is rated as "R-Value." This R-Value is important, but it only works in conjunction with an air or vapor barrier. If, for instance, cold air can pass through or around insulation with a high R-Value, that value is greatly diminished. If the insulation being used is not dense enough to prevent air flow, a means to diminish or stop the flow of air must also be used. Air barrier material is often called "housewrap" and is applied to the outside (referred to as the "cold side") of the house. Housewrap significantly reduces the air flow yet still allows trapped moisture to exit. Plastic sheeting or "poly" is used on the inside ("warm side") of the house to prevent moisture from entering.

What to Look for when Evaluating Your Home

According to James Essig, owner of Expert Insulation, a simple walkthrough can help discover many problem areas. This can be done by the homeowner, but most generally is performed by an insulating contractor or a weatherization expert, who has a trained eye. In the attic, the type and amount of ceiling insulation is determined. Minnesota code requires R-38 for new construction, but going up to R-60 makes sense. Beyond that, there is no gain, either through physics or economic payback over time. Other critical areas are rim joists, rafter tails and cantilevered structures. A very common source of significant heat loss is around recessed lights in the top story ceiling. Holes drilled in the attic for plumbing stacks, vents, electrical wiring, phone, cable and so forth allow air to enter the home. These openings need to be sealed with caulk or insulating foam. Wide open soffit areas are sealed with foam, sheetrocked over or covered with some form of rigid insulation, typically foil-faced rigid foam. Within the house itself, the amount of exterior wall insulation should be determined. Homes built sometime into the 1970s used 2" X 4" exterior walls. After that, 2" X 6" walls were code-mandated. The R-Value of the thicker wall should be at least R-19, with the 2" X 4" walls being closer to R-11. Outlet covers can be removed to see how much insulation is in the walls and also whether air is flowing around the outlets themselves. Another option is to drill a small hole in a discreet area of an exterior wall to see how much insulation there is.

Types of Insulation

The three common types of insulation are fiberglass, cellulose and spray foam. Cellulose is in particle form. Fiberglass comes in either particles or batts. Spray foam is either open cell or closed cell. Both types of foam insulation expand when applied. With cellulose, fiberglass or open cell foam, a vapor barrier is required. With closed cell foam, a vapor barrier is not necessary, since the closed cell product does not allow air or moisture to penetrate and, in fact, becomes rock hard when it dries.

Relative Costs

The least expensive insulation is fiberglass batts, followed by cellulose and fiberglass particles. Open cell foam is more expensive and closed cell foam is the most expensive in this group. Topping the list is a hybrid combination of closed cell foam and fiberglass batt. In evaluating the cost-effectiveness of various insulation options, the factors to consider are current and projected energy costs, costs associated with the upgrade itself and local weather conditions. Additionally, an ethical factor comes into play. Saving energy is just "the right thing to do," regardless of payback timeframes (often referred to as ROI, or Return On Investment).

Insulating Older Exterior Walls

Once it has been determined that the exterior walls need more insulation, there are basically two methods that are used. On an extensive remodel, the interior sheetrock or plasterboard is removed, insulation is applied to the walls and new sheetrock is installed. Sometimes in older homes the exterior walls do have insulation, but it is a kind of shredded cardboard-like fiber that has settled and no longer insulates much of the wall area. In this case, holes the size of a tennis ball are drilled along the top of the outside walls, one for each wall cavity. Each cavity is filled from bottom to top with cellulose, fiberglass or expandable foam insulation. The holes are then sealed, often leaving a round, visible patch on the exterior.


Insulation reduces most of the air infiltration within the home, but does not eliminate it totally. Air can also enter the home around or through leaky windows and doors. A weatherization expert has the equipment necessary to identify and quantify air leaks. "Although most insulation companies can perform a visual inspection of the home,"says Essig, "it makes good sense to work with someone who has the equipment, tools and knowledge to not only evaluate your insulation, but also every aspect of your house’s envelope." There are community action agencies within various counties that now offer energy audits as part of their weatherization programs for certain categories of homeowners.

The Problem of Stale Air

In the "good old days," houses were so leaky that fresh air was always available within them. Now that homes are becoming airtight, breathing recycled air can cause health problems. Air exchangers are used to ensure that there is a constant supply of fresh air, without interfering with the heat balance. The topic of air exchangers goes beyond the scope of this article and may be addressed elsewhere.

A Satisfying Decision

Properly insulating the home makes both environmental and economic sense. The decision to do so results in a comfortable home with lower energy bills and the good feeling of knowing that you are doing your part to reduce the consumption of energy on our planet.

Copyright 2018 Rochester Area Builders, Inc. No part of these articles may be reproduced or printed without written permission from Rochester Area Builders, 108 Elton Hills Lane NW, Rochester, MN 55901. Phone (507) 282-7698.