Hotter weather and a passive house

Extreme weather events are becoming more common, and extreme heat is one part of this picture. Learn about the climate resiliency of a passive home.

The heat dome of 2021 is a very recent memory for many Canadians and Americans, and heading into 2023, we’re looking at more intense heat due to natural planetary cycles combined with the effects of climate change. The US in particular is expected to experience a pretty intense summer for heat and storms according to the Farmer’s Almanac, and much of Canada is also looking at a pretty hot summer, as per media cover like this.

With extreme weather events, some of them causing or occurring alongside power outages, becoming more common, we’re taking some time to highlight how a passive house can perform under these conditions. We’ll dig into outages in our next post.

Building for resilience

Passive homes are different at a fundamental level, as the idea behind them is to build with local climatic conditions in mind. A key principle is to orient a passive home to minimize solar gain in summer and maximize it in winter.

This approach helps to keep the home naturally more cool in the hottest months, and warmer in the colder months. There are variations in heat, cold, and humidity across North America, and we’ll explore that a bit in this article.

The focus on a tight building envelope also means that heat bridges are removed, and heat transfer is minimized, achieving a much more energy efficient and consistent home from a heating and cooling perspective (70% to 90% more efficient than a home built to current code).

Right from the start, then, a passive home is better equipped to deal with the swings between cold and heat that many locales across North America experience.

It’s worth emphasizing that passive house is an international building standard, and it’s designed to work under a wide range of specific climatic conditions. Your EkoBuilt home and its systems can be modified to best work within your climatic zone.

The south facing side of an EkoBuilt passive home is all about the windows.
An EkoBuilt passive home typically maximizes windows on the south-facing side, while reducing them dramatically on all other faces of the home. This helps with strategic solar gain and reduces cost.
This passive home has a screened in porch integrated into the rear, south corner of the building and also includes a small deck.
Any smartly designed home will also take into consideration outdoor living spaces with appropriate shade and protection. More extreme heat should be taken into consideration when planning these spaces.

Neat fact: the cellulose insulation used in our wall assembly works to help keep you cool as well as warm. We often relate insulation to heat, but what it really means is that energy conduction is reduced, keeping warm or cool air inside. This is one of the factors behind the reduced energy demands of a passive home, and one of the reasons why a passive home is so comfortable.

Lower energy demands in winter

EkoBuilt is headquartered in Ottawa, Canada, where temperatures can range from -30C / -22F up to 32C / 90F. More days fall somewhere in the middle, but we’re no stranger to extremes (including outside those ranges) and we’re also prone to some pretty humid conditions.

A conventional home will require active heating 6 to 7 months of the year in Ottawa, 4 to 5 of those months being full time, the rest being intermittent during the shoulder months in spring and fall.

By comparison, an EkoBuilt passive home will only require active heating roughly 3 months of the year. When the sun is shining in the winter, that also reduces the heat requirement to intermittent input rather than constant.

An EkoBuilt home requires very little energy to run in the depths of a cold winter.
An EkoBuilt passive home has a small energy footprint and even uses much less energy for heating in a cold and cloudy winter.

Our passive homes make use of an air source heat pump to handle heating and cooling, as well as an ERV (Energy Recovery Ventilator) or fresh air machine, which also manages humidity.

The heat pump system works well in modestly sized homes typically with a mini split system with wall-mounted registers, allowing for control by “zones” within the home, and optimal energy efficiency.

In very large homes, a ducted system may be recommended instead. As with any client design, we look at the unique factors for your home and make the appropriate recommendations. We also work with local experts to determine the best approach to factors like roofing for snowloads or approaches to exceptional humidity (noted below).

Read about the mechanical systems we use.

Lower energy demands in summer

We can flip that scenario when talking about, for example, a property in the southern United States where there is heavy reliance on air conditioning to get through many months.

In the same way that the energy demand of one our passive homes is much lesser under cold winter conditions, it will also be correspondingly less for a home that relies more on cooling cycles to stay comfortable.

Depending on the severity of heat being experienced, it may only be necessary to have active cooling take place from one to six hours per day.

It’s worth noting that what we experience as comfortable room temperature, varies. In the winter, 21C / 70F is often considered to feel just right, whereas in summer it’s closer to 25C / 77F. Humidity will also affect this number.

An EkoBuilt passive home can be modified to work optimally under local climatic conditions. See all of our house plans.

Optimal humidity levels tend to fall between 30 and 60%. If you live in a location where humidity is often much higher and homeowners tend to require additional de-humidification systems, it will likely be the case that we’ll want to build in additional measures to counter humidity. We can do that!

Year round comfort

Comfort, health, and efficiency are hallmarks of a passive home all year round. As local climatic conditions continue to be pushed towards extremes, we can work with you to tweak your passive home for maximum performance and comfort.

Ready to discuss your project? Just give us a shout!

2 thoughts on “Hotter weather and a passive house

  1. I was originally worried our Passive House would be too hot back in the day before PH was a big thing. There wasn’t much info online back when I built our first PH home. Even with so much insulation and a high performance air-tight construction it’s just as comfortable in the summer as it is in the winter. Having operable windows at night helps.

Leave a Reply