The long-term financial and health benefits energy-efficient design
Home heating and air-conditioning accounts for roughly half of the total energy usage in the average U.S. home. And in the Maryland and DC-Metro area, many households experienced record utility bills over the winter of 2025-26, due to an extended deep freeze that is uncommon for this region. With energy costs rising and the grid being stressed to its limits, the financial incentive to improve home energy efficiency continues to grow.
By reducing household energy needs through better design and energy efficiency upgrades, you are effectively paying yourself back for money that would otherwise have been going to the utility companies, for as long as you own the home. And as a bonus, these improvements generally enhance indoor air quality and thermal comfort.
A big challenge to overcome is that most existing homes are not designed to be able to regulate temperature without substantial energy input from the grid. The high-maintenance HVAC systems struggle to maintain a stable and comfortable temperature, especially during weather extremes.
Why air temperature alone doesn’t result in thermal comfort
I used to think that maintaining a comfortable indoor environment was about controlling the air temperature. It’s a reasonable assumption given that most U.S. households use ductwork to move conditioned air throughout the home. But my experience living in a top floor apartment in an old NYC walk-up building taught me that air temperature is only part of the equation.
The building we lived in had a black tar roof. Its dark color and high thermal mass made it a very effective heat sink. Apparently these roofs can approach 190°F during the summer! Not the ideal situation if you're trying to keep the building cool.
After the sun went down, the roof would continue to release the stored heat for hours, some of which would pass through our ceiling and radiate into our apartment. Even with the window A/C unit on full blast in our small ~70sqft bedroom, I would still be sweating through the night. The lack of sufficient insulation above the ceiling and the heat-accumulating properties of the roof made it impossible to maintain a comfortable temperature on the hottest days.
On the other hand, the apartment was actually very comfortable in the winter, being heated with a combination of a steam radiator and the winter sun that poured in through the south-facing windows.
This made me realize that forced-air heating and cooling systems are not an effective means on their own to create a feeling of thermal comfort. To understand why forced-air systems struggle during temperature extremes, we need to understand the three ways that heat moves through a home.
What exactly is thermal comfort? “The Passive Solar Energy Book” by Edward Mazria summarizes the concept beautifully:
“The question of comfort depends primarily on the maintenance of a thermal environment in which the body can lose heat at a rate equal to its production without the need to sweat on the one hand or shiver on the other.”
Heat moves through a home in three ways
Below is a brief summary of how heat moves through a home via conduction, radiation, and convection. Apologies to the engineers for any oversimplifications!
Conduction is the transfer of heat via direct contact.
Think bare feet on a cold tile floor or a hand touching a hot skillet. Wall studs will conduct heat into or out of the home if continuous insulation is not installed in the building envelope. Dense materials such as ceramic, stone, iron, and water have a high thermal conductivity. Insulating materials, such as wool, foam, and cellulose insulation have a low thermal conductivity and slow the transfer of heat.
Convection is the transfer of heat via the movement of a fluid such as air.
Conventional HVAC systems, heat pumps, mini-splits, and window A/C units work by circulating heated or cooled air through a home. Natural ventilation is also a type of convection.
This air movement associated with forced-air systems also promotes evaporative cooling and reduces humidity. This is a benefit during hot and humid summers, but can be a drawback during the winter when we are trying to stay warm and hydrated. An excessively low-humidity indoor environment will tend to dry out our skin and respiratory tract, leaving us more vulnerable to infection. This issue can be exacerbated if the ducts and air filters are not well maintained, increasing the potential of dust, pollen, or mold spores becoming airborne.
Radiation is the transfer of heat through space between two objects within the line of sight of each other.
Woodstoves, infrared saunas, radiators, and the sun are sources of radiant heat. Radiant floors actually transfer heat via radiation and conduction if you are standing on them.
You’ll feel the effects of radiant cooling when standing in front of a single-pane window when it's cold outside or when near a high thermal mass interior wall (clay, stone, concrete) that stays shaded from the sun. It effectively acts as a heat sink, drawing heat from the surroundings and nearby occupants.
Mean radiant temperature affects body heat more than air temperature
The mean radiant temperature (MRT) is the average of all the surface temperatures in a given space. This includes the walls, windows, floor, ceiling, and any other large structures.
A 1°F change in MRT has a 40% greater effect on body heat loss/gain compared to the same 1°F change in air temperature.
This means that at an MRT of 65°F, the air temperature would need to be 77°F to result in a feeling of 70°F. This would be ideal in the summer, but would result in a crazy electric bill in the winter! This is one of the reasons that relying solely on forced-air heating and cooling is an inefficient way of maintaining a comfortable indoor environment.
Achieving thermal comfort at a lower cost
While installing solar panels to generate your own electricity is great, they are even more effective when combined with an energy efficient home. After all, the easiest way to cover your energy needs, is to not need much in the first place!
Each home and its setting is unique, but the following energy-saving strategies should prove beneficial for any home in our Mid-Atlantic climate:
1) The building envelope must have sufficient insulation and air sealing.
The building envelope consists of the walls, foundation and roof that separate the interior from the exterior environment. A high-performing building envelope is necessary to prevent draftiness and heat loss in the winter, and excessive heat gain in the summer.
Insulation requirements were first implemented in 1965, and began to rise starting in the late 1970s, partially in response to the 1973 oil embargo. Over the years the insulation minimums continued to increase, and the guidelines adopted in 2012 largely still meet the current requirements. So when shopping for pre 2012 homes, know that there's a greater potential to find a building envelope that is trailing today’s standards.
That being said, the standards are just minimums, not necessarily optimal amounts. Performing an energy audit will identify air leakages and insulation deficiencies and is a smart idea regardless of the age of the home.
2) Use proper solar orientation and high thermal mass materials to benefit from passive solar heating
When the low winter sun is able to stream into a home, it warms the interior very effectively, and not to mention it brightens up the space during a time of year when we need all the sunlight we can get. And if the sun’s rays hit a high thermal-mass material (e.g. a concrete or brick wall), the heat will be absorbed throughout the day and then gradually released to the surroundings at night. This is one of the primary concepts of passive solar design.
During the summer, keeping the interior shaded from the hot midday and afternoon sun to reduce solar heat gain and limit or eliminate the need for air conditioning. Shading devices could be a roof overhang that shades the exterior walls from the high summer sun, or something as simple as solar window shades. A mass wall is also a benefit for cooling purposes, as it will draw heat out of the air as long as it stays shaded during the warmer months.
Ideally the home is designed with the proper solar orientation from the start, but if not, retrofitting with strategically placed windows, skylights, or even an attached greenhouse can be effective methods of both capturing solar heat and shielding it when necessary.
3) Use plants to improve your micro-climate
Plants have an amazing ability to cool a home! A large shade tree to the west will protect a home from the hot afternoon sun and will provide a layer of cool air in the yard. A trellis that shades an exterior wall with a leafy vine is another effective way to provide shade.
Green roofs provide another natural cooling method. Plants will actively cool the roof via evapotranspiration through their leaves. It’s a viable option so long as the roof is engineered to support the additional weight.
Having a dense evergreen hedge that acts as a windbreak will also reduce heat loss in the winter, particularly if it is positioned to the north and west of the home to block cold winter winds.
Buying and Selling Energy Efficient Homes in Maryland & Washington D.C.
The rising cost of energy currently outpaces inflation for Maryland and DC households, and all signs point to this trend continuing.
Before purchasing a home, you may have the opportunity to see the previous year’s electric and heat bills. While this is a useful data point, there’s no guarantee that the previous level of energy usage actually created an indoor climate you would be comfortable in, so I’d take this info with a grain of salt.
Although energy efficient homes provide financial, health and quality of life benefits, they remain undervalued in the marketplace. This may change over the coming years, but I'm not holding my breath!
This creates an opportunity for those who are buying or selling homes and are able to recognize the long-term value of energy efficient design.