A Home’s Thermal Envelope
Did you know your home’s thermal envelope is essential to its ability to maintain a comfortable temperature in all weather? Read on to learn more!
It’s been extremely cold out! How is your thermal envelope?
In Ohio we are fortunate to get a taste of all four seasons. Our average lows can be 20 degrees or lower in the winter and our average highs can be 90 degrees or higher in the summer. Spring and fall, well sometimes those happen. Comfort and energy (financial) efficiency require your home to have a suitable thermal envelope. Let’s explore.
What is a thermal envelope?
A thermal envelope is a component of the building envelope. Essentially, the building envelope is the parts of a home that protect or mitigate and attempt to control the interior space from the exterior environment. This includes water, air-borne pollution, light, noise, and temperature.
The parts of the home that influence temperature comprise the thermal envelope. When discussing thermal envelopes you may also hear it described as separating conditioned space from unconditioned space. Conditioned space is anywhere in the home that is heated or cooled. Conditioned space typically is all of the inside space except the attic and the garage (it is still common for crawl spaces to be unconditioned but it is recommended to seal and condition those if possible).
The heat generated in your home is transferred three different ways, convection, conduction, and radiation. Primarily we are concerned about convection, the transfer of heat by a gas or liquid, thus thermal envelopes are also impacted and rely on moisture and air-flow control, and conduction or the transfer of heat through solid materials.
What are the typical components of your thermal envelope?
The structure of a home: foundation, walls, floors, ceilings
Insulation
Vapor barriers
Exterior doors
Windows
Exterior vents
Weather stripping
A note on stack effect and cold weather.
In the winter, a significant portion of heat loss is due to the naturally occurring phenomenon called stack effect. Stack effect is the movement of air into and out of buildings. Warmer air naturally rises above colder air. In a heated home during cold weather, the warm interior air is always looking for a way to rise up, continuing to rise until it ultimately finds a way out of the building. This exiting air is replaced by cold air entering the building at lower levels. The colder air typically enters around foundations, doors, and windows, but will ultimately take advantage of any opening to flow into the house. The stack effect also impacts air conditioning but generally less.
Some things that can help your heating comfort and efficiency.
Drafty door? Seal it with weather stripping or use draft blockers.
Is your attic access inside your living space? Make sure it is well insulated, poorly insulated attic hatches allow an easy path for both heating and moisture to escape.
Are your chimney flue dampers closed when not in use? This is another express lane for conditioned air if left open all the time.
Are you getting maximum efficiency from the warm air in your house? Ensuring your ceiling fans are running on low and the appropriate direction (clockwise) during the winter can help maximize the use of the heated air by cycling the warm air stuck on your ceilings.
Small changes can have large impacts for air movement and moisture control. Make sure you aren’t letting the easy fixes keep you in the cold!