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Insulating structural masonry (brick on block) homes

Rarely a week goes by that I don’t receive a phone call from a client who lives in a true masonry constructed home. As with any home, the most common complaints are uncomfortable rooms and high energy bills.

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How to make a structural masonry home more energy efficient.

Rarely a week goes by that I don’t receive a phone call from a client who lives in a true masonry constructed home. As with any home, the most common complaints are uncomfortable rooms and high energy bills. Often the owners are simply seeking advice and asking about my services, but more often than I like, the clients have already had “contractors” to the home to preform insulation upgrades or retrofits that haven’t worked as promised. Hence the purpose of this post!

Masonry constructed homes were popular up through the 1950’s. These aren’t your common “stick-built” wood framed homes, and have some unique features that require careful consideration before embarking on any home improvements. These types of structures are either true 2 or 3 wythe brick structural masonry homes -or- what is commonly referred to as masonry cavity “brick-on-block” construction.

The latter is built with 8 inch wide concrete masonry units (or commonly referred to as “cinder” blocks) as the structural component, with a single layer brick veneer wall exterior.

In both types of masonry construction the interior plaster walls are attached to thin wood furring strips (typically ¾ to 1 inch thick) anchored to the structural wall (brick or block).

In masonry cavity (block wall) construction a 1 inch gap is purposely left between the brick and the block to provide a drainage plane for any potential water ingress through the brick to drain out. The structural component is the 8 inch concrete block rather than traditional wood framing we are commonly accustomed to.

Unless solid foam panels were added during construction (not common), there is no insulation in the walls.

Structural masonry wall viewed from attic
Structural masonry closeup - block on left, brick on right, air gap in center
Uninsulated structural masonry infrared view from interior

Energy costs and today’s insulation standards were not much of a consideration back when these homes were constructed. Surprisingly, the thermal mass of masonry walls is considered very efficient in many arid and moderate climates as the dense masonry materials increase the amount of time required to transfer heat energy.

Fast forward to today where energy costs have risen exponentially, place the home in a climate where average daily temperatures reside in the single digits for weeks if not months during the winter, and we have a recipe for owner frustration and angst.

All is not lost if the owner of such a home can do their homework! In almost all cases, it is neither feasible nor financially justifiable to try and insulate the walls of these homes. There simply isn’t any room designed into the wall structure to allow for adequate insulation.

Unless one is planning significant interior renovations and additional framing can be included, then the financial and corporal return on investment for adding or retrofitting insulation is simply nonexistent.

Additionally, we run into the problem of reducing interior living area by traditionally framing out the perimeter walls.

Where existing owners really run into issues is when they follow the misinformation and ill advice from some unscrupulous insulation contractors who claim their injected foam insulation product can solve their woes with minimal effort.

Injected foam insulation failure
Injected foam insulation failure

These contractors and their fast talking salesmen claim that the deliberately designed 1 inch air gap between the brick and the block is the prefect and ideal place to inject their foam product. They couldn’t be more incorrect and treacherous in their recommendations.

As stated earlier, this air gap is intentionally designed to provide a drainage plane for water that WILL migrate through the masonry wall assembly. Filling this air gap with anything other than air can have devastating consequences, especially when water does migrate and has nowhere to go.

In freezing climates, substantial and costly damage can occur due to frost action when water is trapped in the masonry wall. Additionally, many of these injected foam products do not hold up well in damp or moist environments. If it gets wet, the product breaks down losing practically all of the insulating and air barrier qualities that originally sold you on the product!

Deteriorated (crumbling powder) foam insulation
Infrared view of deteriorated foam insulation (dark areas depict cold temperatures)
Severe frost/freeze damage at exterior brick caused by foam insulation retaining moisture in the masonry cavity

The purposely incorporated air gap in the walls of these homes connects to the unconditioned attic where air freely travels through this unhindered bypass… as it should.

Once the air gap is obstructed, airflow will find the path of least resistance which is typically to the interior plaster or drywall gap.

As seen in these thermal images (below) from homes retrofitted with foam insulation, cold air is now freely flowing (bypassing) from the tops of the interior walls down.

This is the most common complaint from structural masonry home owners after an insulation retrofit – cold air drafts!

Examples of airflow (air migration) down interior walls of structural masonry home after wall foam insulation retrofit in air gap cavity

This brings me to arguably the most prudent energy efficiency upgrade available for structural masonry homes… Air Sealing.

Gaps are present where perimeter and interior walls meet attic spaces and the foundation sill plates and rim joists.

Because wall insulation is not a good investment for these types of homes, and can actually be detrimental as stated previously, attacking the home’s air infiltration issues often provides the best return on investment.

Air sealing (blocking) should occur from above and below, meaning from the attic and foundation.

Even in current construction practices for stick-built homes, these areas are the most overlooked for installing air blocking measures. Simply installing loose insulation such as fiberglass batt is a losing proposition.

 

The common misconception is that all insulation stops airflow. Quite the contrary, loose fill or batt insulation simply creates an air filter. Meaning you no longer have dirty cold air drafts occurring throughout the home, you simply have clean cold air drafts.

Don’t believe me?

Next time you enter the attic for those old family photos, pull back some of that insulation laying over the kitchen wall or around the plumbing vent stack penetration through the ceiling and see just how dirty it is!

Airflow resulting in dirty insulation at ceiling/attic penetration

The best choices for air sealing these areas includes cut-to-fit rigid foam boards sealed with caulk or construction glue, or spray applied expanding foam insulation (the closed cell type). These areas must be completely blocked to prevent airflow. Some good “How to” guides can be viewed at Insulate Basement Rim Joists Guide and Attic Air Sealing Guide and EnergyStar DIY Guide

Expanding Foam
Rigid insulation

Once this is performed, then it’s time to address the rest of the drafts in the home. This includes cover plates at wall receptacles and switches (with pre-cut foam gaskets), gaps at trim joints (foam backer rod, caulk, or expanding foam at baseboard and window trim), and window/door weather-stripping. Additional informative guides and tips can be viewed at Sealing Your Home Guide

Air migration at baseboard trim
Air bypass at entry door

Most of these home improvements can be done for relatively low cost and light to moderate labor.  Air sealing improvements can be performed on ALL home types regardless of construction, but are especially prudent for structural masonry homes. 

Be advised for safety purposes though, if significant air sealing is performed in your home, PLEASE have a professional technician thoroughly evaluate ALL combustion appliances in the home to make sure they are operating safely and efficiently.  Major air sealing efforts will improve your comfort levels and overall energy use, but can dangerously affect the natural exhaust drafts and combustion air provisions for such appliances.

If you need help identifying sources of air leaks, insulation deficiencies, or simply need guidance on improving your home’s comfort levels and energy use, BC Warner Inspections provides this service as an unbiased evaluation of your home. For more information on this service please visit http://www.daytonthermalinspection.com/dayton-energy-audit.html

If you own a structural masonry home, I hope these tips have provided you with some assistance and direction, as well as prevent some expensive misguided mistakes marketed by unprincipled insulation “con-tractors”.

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