Defining comfort and designing for it

Zero Energy House

The core reason Shay Brazier and Jo Woods chose to build a house was because they wanted a home that was comfortable to live in. Refusing to believe that a house either had to be good for the environment or comfortable for its inhabitants, the couple knew they could achieve both these things through the use of good design and the right products.

Setting comfort goals

People’s understanding of comfort is often vague and subjective, it means different things for different people. In an effort to articulate just what comfort meant for them, Shay and Jo set three broad comfort goals for the design of the Zero Energy House:

  • Achieve a stable internal temperature range as winter temperatures outside dropped significantly overnight.
  • Achieve consistency of temperatures between the living and bedroom areas, so the house would be warm throughout.
  • Achieve the above using passive design strategies, avoiding the use of mechanical heating or cooling systems.

Additionally, they defined an acceptable temperature and humidity range for the house (see table below) guided by recognised standards on human comfort, but ultimately determined by a deep understanding of what felt right for them. The expectation was that this range would be met 95% of the occupied time.

These comfort goals were communicated to the design team in the Design Brief and tracked during the design process using thermal modelling.

What exactly is comfort?

Shay and Jo’s experience in the field of building design meant they had a clear understanding of what comfort was and of the impacts it could have on people. However, figuring out what comfort means is not always easy. In general terms comfort is defined as a state of physical ease and it’s influenced by a number of factors. The Center for the Built Environment has an online tool to calculate comfort levels based on six variables:

  1. Air temperature. Temperature of surrounding air, shielded from radiation and moisture.
  2. Radiant temperature. Temperature radiating from surrounding objects.
  3. Humidity. Amount of water vapour in the air.
  4. Air speed. Rate of movement of air.
  5. Metabolic rates. Varies from person-to-person and activity-to-activity.
  6. Clothing level.

Designing for comfort

Out of the six variables that define comfort, the first four are environmental and are addressed at the Zero Energy House through design and the products used:

  • Temperatures and humidity are monitored by sensors and controlled through passive solar design. Heat is captured during the day in the ground-floor concrete slab and then released overnight. This heat is retained within the house by an extremely efficient building envelope, which has a double layer of insulation and high-performance glazing. The thermal mass and building envelope work together to keep temperatures relatively stable during the day and at night.
  • Air speed is controlled, again, by a tight building envelope and the ability to manually adjust ventilation levels through the dual-tilt windows installed.

The last two factors on the list are related to people. For example, a duvet at night will increase a person’s clothing level, which means the air temperature can be slightly cooler without changing the degree of comfort.

Articulating what comfort meant to them and translating that understanding into qualitative and quantitative goals for the Zero Energy House, allowed Shay and Jo to communicate their expectations around comfort to the design team and keep track of them during the design. In the end, the best proof of their success is having a comfortable home built without compromising their ideals.

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