Interior Rehab with InSoFast over Masonry Walls

In a recent This Old House Q & A, a homeowner was looking for answers on how to insulate his 1950s brick colonial home. The concrete block walls were completely void of insulation.

In response to his question, Tom Silva bluntly states that concrete block walls are “the perfect application for InSoFast foam panels”. Silva suggests that the best way to address this chilly problem would be to “cover the inside of the exterior walls with a continuous layer of insulation”, just as you would with a basement wall.


It’s frighteningly common for older homes to be void of insulation altogether. In fact, insulation didn’t become an aspect of building codes until as late as the 1970’s. Achieving a higher R-value basically meant building a thicker wall. As John Straube of Green Building Advisor puts it, “in the old days, when we didn’t have good structural engineers, to be able to build a building you had to use a lot of material — and it had to be solid.”

Consider all those 19th century brick beauties that made up the majority of North America’s early industrial cities. The heyday of solid craftsmanship is still prevalent in places like Chicago, New York, Philadelphia, Toronto, St. Louis. These homes and buildings were structured to withstand centuries, yet many of them still suffer from R-values nearest to nothing when compared to today’s standards.

In the case of the Q + A, Silva points out that the homeowner’s masonry walls probably, “have an R-rating of about 3” but need a value of at least 10. By adding InSoFast panels, the R-value of the walls will raise to R-13, which is a whopping “30 percent more than the IECC minimum”. It is also a life-changing increase in comfort.


If your home’s walls are poorly insulated 2x4s, InSoFast panels can save time and money by being added directly over top. The space-saving design does not even require tearing out old lath and plaster. Our panels can be glued directly to concrete block making the installation process a whole lot easier for all types of masonry homes, which is what Jeremy and Melissa discovered nearly 5 years ago.

Back in 2011 Jeremy and his family bought a beautiful two story brick home in Minnesota. The exterior of the 19th century masonry structure was in great shape but the interior was in serious need of a retrofit. With the occasional help of family members, Jeremy and his wife Melissa insulated the entire interior with InSoFast UX 2.0 Panels. We recently caught up with Jeremy who talked about his project, the installation and the state of his home nearly 5 years later.

Back in 2011 your 1880’s brick style home was in classic need of an energy retrofit. That’s when you made the decision to insulate the interior masonry walls with InSoFast UX 2.0. Can you talk about the pre-existing conditions of your home before the retrofit?

We bought the house as a foreclosure, so we got it for pretty cheap. The house would have been livable but there were some major repairs that needed to be done in the bathroom and throughout the house, so we decided to just remodel the entire thing before we even moved in. We didn’t want to live in a construction zone.


We completely remodeled the entire house. We squared out all the walls and the old lath and plaster. Everything else got replaced including the stairs, plumbing, electrical and all of the duct work. I put in a new furnace and water heater. It was a big project. We decided to insulate since we were starting from square one. The house didn’t have any insulation in the outside walls, just brick.

Let’s talk about the installation. We heard you had the whole family working together for the project. How did it go?

Ed from InSoFast actually came out the first day and helped us get started with the project. Just in that first day my wife and I finished a few walls with the help of Ed. We installed the rest of the panels ourselves in between working and all that other life stuff. It ended up taking us a whole year to get the entire project done, but the insulation went really fast. My wife, mother-in-law and my dad were all involved in getting the insulation on the walls.


It went really well and was incredibly easy. My wife and mother-in-law didn’t have any kind of construction background but they were installing the panels just as fast as my dad and I in the other room.

That’s great to hear. So was the speedy process the main reason you chose InSoFast?

We had looked at other insulation options like spray foam but since we were working with brick walls, we wanted something that would adhere to the walls. If we had chosen spray foam we would have had to build walls for the spray foam. Then we would have had to hire a crew to come in and spray. It was just a lot more work.

Cost and time wise it made sense to go with InSoFast. Also, InSoFast saved us a little bit of room. If we had furred the walls out for the spray foam our house would have been that much smaller on each side.

In order to use the panels you had get approval from your local building inspector. Did you face any challenges with this process?

Nope. I called him up and talked about InSoFast. He asked if he could see the panels, so he came out to take a look at the panels and approved the project right away.

It’s been nearly 5 years since the retrofit. Your family has had some quality time to feel the impact. How has the update changed the comfort of the home?

It’s been good. Since we updated everything before we ever lived in the house it’s hard say. I do know that when we were doing the construction of the house it was wintertime here in Minnesota. After installing the new windows and the InSoFast there was a noticeable change in the temperature of the house. We stayed much warmer during the rest of the construction process.


It’s important to remember that the lack of insulation in masonry built homes is especially problematic considering the presence of radiant heat. Brick and concrete block hold onto this ambient temperature which has a pretty big influence on comfort regardless of how much the heat is cranked up. Without insulation your masonry walls will literally feel cold. Additionally, a convective loop of warmth from the interior walls will flow over to the cooler exterior walls creating a draft.

InSoFast solves this problem by creating a continuous buffer that reduces the radiant cold seeping from masonry walls. The tongue and groove edges built into our panels form an interlock that prevents thermal bridging. Instead of heating up that 9” thick masonry wall you heat the actual air in the room. In effect you’ll see an increase in comfort and some extra cash in your reserves. Take it from Mr. Silva (aka: ‘contractor-guru-extraordinaire’), “when you’re done [insulating], I bet you’ll see a welcome drop in your heating and cooling bills”.

  • Katherine

    Great job! I can echo so much that was written about the InSoFast insulation panels for Jeremy’s home in MN. We, too, have a concrete block home… in MA. No bricks over the blocks. Just decorative-looking blocks. Our house was built early 1900s. The only thing inside the block walls are furring strips, wood lath, and plaster. This year we remodeled our kitchen, along with an adjacent laundry room and a bathroom. As the exterior walls for the laundry and bath face North, those rooms were always very cold during the winter months. In fact, we could feel the radiating cold well into the kitchen. (One year we tried closing off the laundry, only to find that the radiating cold caused the water line to the washer to freeze.) We couldn’t afford to give up all the floor space that would have been lost had we framed inside the block wall, so I was thrilled when I read about InSoFast panels in “This Old House” magazine. I ordered enough panels to insulate our North-facing bath and laundry walls, and had our contractor remove all of the old plaster and lath, leaving just the block walls. The lath and plaster was about 1-1/2″ thick, so we lost only about an inch more of floor space, after having the 2″ InSoFast panels and 1/2″ drywall installed. I’m anxious to learn the full difference that the InSoFast panels will make this winter. Thus far, we’ve had a few mornings when the outdoor temp has dipped below freezing, but these North-facing walls feel no colder than our interior house walls. What a difference! We’re hoping to be able to insulate more of our exterior walls with this great product in the coming year.

  • David Goddard

    Are the studs in insofast discoverable by a standdard stud finder?

    • They are, just like any normal stud.

      • David Goddard

        great thanks. I think my code requires R13 (zone 4a). Will my poured concrete walls + insofast + drywall meet that?

        • Our EX 2.5 panels are R13 equivalent by way of their continuous profile. In order to make sure that’s what you need, we recommend checking out this website on IECC Climate Zones and code adoption status. It’s also a good idea to ask a local building official for county-level specifics. You may need less!

          You can find more information on our panels’ thermal performance on the Technical pages of our website.

      • David Goddard

        If i put insofast plus over the panels, will a stud finder still find the integrated studs?

        • While there are different types of stud sensors available, most are designed to detect density changes across a wall. In general, the stud will be a denser material than the surrounding wall space, which is typically air or insulation. This is the case in the InSoFast panel where the thick polyproylene stud registers as more dense than its EPS foam body.

          The concept will be the same in a PLUS system. A calibrated sensor will notice areas of foam and drywall having less density than an area of the same materials that also contains the InSoFast stud. To get an accurate reading in a PLUS system, you’ll simply need a sensor that can reach to the depth of the stud. The biggest downfall here will be what you spend on the $tud $en$or…

          Keep in mind that the InSoFast studs are located exactly 16″ O.C. which means you only need to know the location of one stud (for instance, 16″ from the corner) to be able to find the rest by measurement. We like to keep it simple and affordable, which is why our favorite “stud sensor” is a good, strong magnet (see: neodymium). Once your walls are covered, you can slide the magnet around till it snaps onto a metal screw holding up your finish. That’s the location of Stud No. 1, the rest are 16″ apart.