How to Improve the Comfort of Your Midcentury Modern Wood House

Why  midcentury modern homes fell out of fashion in the 1970s was that their thermal performance was so poor. Midcentury modern design was fashion in aesthetics, but it also turned out to be beyond the technical performance of the materials available to designers and home builders. The spike in energy prices in the mid-1970s was a knockout punch, making these homes so expensive to heat and cool that homeowners had the difficult trade-off of paying exorbitant utility bills or stocking up on sweaters in the winter.

Aside from the heating and cooling costs, the homes tend to be uncomfortable because of drafty walls and windows and cold pockets due to inadequate mechanical systems. Here are some tips to improve the comfort of your midcentury modern home without losing any of the design vibe.

Update Windows

Extensive glass areas are a key feature of midcentury modern homes, providing sunlit interiors and a powerful connection between inside and out. All of this glass comes at a cost, however, adding dramatically to the heating and cooling loads. This is magnified when the glass areas are oriented to the north, away from the sun, offering only thermal loss in the winter, or oriented west, leading to excessive heating by the setting sun in the summer. Add to this the fact that many homes from the era still retain the original single-pane windows.

Window tech has come a long way, with double or triple glazing readily available with argon gas, achieving much improved insulation. To prevent heat gain, glass coatings called “low-e” have been developed to prevent the sun’s radiant heat from penetrating the glass.

The window frame is also important, as having a good thermal break between inside and out is critical. Take this midcentury modern remodel in Los Angeles done by JA Design. Much of the work involved the addition of windows to open up the space and improve sightlines to the ocean. With today’s technologies, this was possible to achieve without compromising the home’s design.

The original metal windows of midcentury modern houses have crisp sightlines and slim profiles. A few companies are now offering thermally broken steel windows that offer minimal sightlines and good thermal performance, including Hope’s and Brombal.

Insulate for Comfort

One of the beauties of midcentury modern homes was the modernist idea of exposing the home’s structural posts and beams. This was a refreshing change from traditional house design that covered the structure with wallboard and trim. While attractive, exposing the structural members precludes using the space between the beams for insulation.

Exposed rafter ceilings. Exposed rafters are a key component of many midcentury modern designs. In order to preserve the beauty of this design feature, insulation needs to be added above the ceiling.

A great approach is to use rigid foam board along with an air barrier above the ceiling. The interior appearance is not compromised, and a high level of insulation is achieved. This approach also solves a problem seen in snowy regions, where heat can escape through the roof, unevenly melting the snow and causing ice dams.

Walls. When structural posts are exposed, the main challenge is preventing air seepage where the posts meet the walls, such as in this midcentury home in the Bay Area renovated by Koch Architects. New spray foam products are highly effective in addressing this. Closed-cell spray foam can seal the air gap between the post and wall, along with filling the cavity between posts.

The concept of radiant floor heat dates back to the Romans. The standard approach is to place a loop of tubing in the concrete floor slab and then run hot water through the coils to heat the floor and provide heat to the room. When done well, it is one of the most comfortable sources of heat.

In midcentury modern homes there often were flaws in the way the radiant heat was installed, leading to poor performance or failure. Typically, the radiant heating tubes were buried deep in the floor slab without insulation below. Not only is heat lost to the earth, but it’s also difficult to control.

Now, the best practice is to place the heating tubes on top of the concrete slab with a layer of insulation between the heating coils and the concrete slab. This keeps the heat from being lost into the concrete slab, vastly increasing its efficiency.

A related challenge is the design of the concrete slab itself. In the midcentury modern era, the concrete slab was poured directly on the ground. The new approach is to waterproof the bottom of the slab and install insulation there. This keeps the slab close to the temperature of the interior of the house, which is very important in summer to prevent condensation on the slab and attendant mold.

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