Older home on wooded lot
Energy Efficiency, Passive House, Passive House facts, Retrofitting Older Homes

Retrofitting an older home to Passive House standard

Next stop in our new series on retrofitting older homes: changes to attain Passive House standard. We have received many requests from readers on how to transform an existing home into a passive home.

Everyone who follows this blog is aware that our mission is to build passive whenever we can. Building to PassiveHouse standard makes the home environment healthy, therefore translating into healthy living. It also makes the world a much healthier place as our dependency on petroleum-based fuels as heating and cooling sources is removed. Finally, a passive house is much cheaper to run. You can think of a passive house as the domestic equivalent of an electric vehicle.

IPHA guidelines

EkoBuilt follows the guidelines from the International Passive House Association. There is a lot of building science behind passive, so it can get very complicated, but it can also be explained and understood very simply. From a build perspective, the world is slowly transforming to become completely passive. Certain areas of British Columbia already mandate the passive standard in order to qualify for a new building permit. It’s important for everyone to understand as it will be here in Ontario sooner than we think.

Passive House Explained in 90 Seconds from Hans-Jörn Eich on Vimeo.

The video was made by Hans-Jörn Eich, a certified Passive House Consultant (Passivhaus Institute in Darmstadt, Germany) and the founder of Pinwheel.

Why does passive house exist?

It’s simple: to replace heating and cooling dependency on gas with electricity. That said, this is only economical if the heating/cooling demand can be reduced to a point where it’s inexpensive to use electricity, and this is where design essentials come into play.

There are three essential design features in a passive home:

1. Air-tightness

It’s vitally important that heat loss is minimized through unwanted and unnecessary leakage of air. We conduct what’s called a blower door test to find the ACH (air changes per hour) a home experiences.

Most newly built homes experience ACH anywhere between 3 and 5, meaning 3 to 5 times the entire volume of air inside the home escapes each hour. This is basically a loss of heated and cooled air which can also result in condensation in the wall cavities, translating ultimately to unhealthy mold.

For newly built passive homes, the ACH rate is 0.6 and the retrofit standard is 1.0.

Old school thinking favoured this air loss, thinking it good for fresh air to enter the building and provide a natural fresh air environment. We now know this is laughable because of all the mold problems we’ve heard about with older homes. To be fair to the old schoolers, in the past, modern building techniques/methods did not exist, nor did heat recovery ventilators (HRVs), so the options didn’t exist to change this approach.

Modern building code recognizes this fundamental change. For example, since 2017 Ontario building code has made HRVs mandatory in all homes, which we were thrilled to see happen. The problem is the HRV is only required to be 50% efficient and most homes are still leaking more air than they should.

2. Thermal envelope

Currently new-build homes, according to the standard building code, are required to have R22 wall insulation, R32 roof insulation and R10 below slab insulation. By comparison, in our local area, newly built passive homes require R75 wall insulation, R110 roof insulation and R40 below slab insulation.

As a general rule of thumb, homes retrofitted to passive standard require R48 wall, roof and below slab (or floor) insulation.

3. Proper windows

For thermal comfort, it’s very important that a passive approved window is used. These are triple glazed units with insulated frames equivalent to an R12. This may not seem like much, but compared to a non-certified triple glazed window, it’s huge. With non-certified units, it’s hard to find a unit above an R4 rating.

Certified windows optimize comfort by having a high temperature interior pane (instead of being cold on the inside when it is cold on the outside). In the passive scenario, this means when it is 25°C outside, the interior pane must be at least 17°C. Non-certified triple glazed windows can be as low as 12°C on the inside under the same conditions.

For those who would like the complete building science, please have a look at the following 20-page document, Criteria for the Passive House, EnerPHit and PHI Low Energy Building Standard (pdf). You can also view four charts at the end of this article.

How can an older home become Passive?

With all of that out of the way, how does an existing home reach the Passive standard?

To be achieved in the most cost-effective manner, this approach will obviously vary depending on the home in question, but some general rules apply:

For the walls: Airtight/vapor tight permeable layers and extra insulation will need to be installed. This will mean that either the interior or exterior finish will need to be removed (the choice will usually depend on which is most cost-effective). Certified windows and doors will also be sourced.

For the roof: If the home has an attic space (most do), extra insulation will be added to that space with an airtight/vapor tight permeable membrane installed on the ceiling side. If there is no attic, then an extra thermal later will have to be installed on the interior. If the ceiling is cathedral in design, it should be simple to build the ceiling down to the required R value. If the ceiling is flat and losing height is an issue, than a vacuum panel will be used to provide a thermal barrier with minimal loss in ceiling height.

For the slab/floor:  If a basement is unavailable/unusable, then a thermal layer will be added to the existing floor cavity. If a basement is present and usable, a vacuum panel will be used to provide the thermal barrier with minimal loss in height.

Interested in making your existing/older home Passive? Give us a shout, we’d love to help you realize that goal.

You may also be interested in our blog post on taking a staged approach to retrofitting your older home.

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2 thoughts on “Retrofitting an older home to Passive House standard

  1. Don Gibbons

    So where is the ‘sweet spot’? In the production of the insulation materials, a lot of CO2 is released. How much CO2 is being conserved with the insulation levels versus how much CO2 is released in their production? What’s the ‘payback’ period? As a home designer, this is something I’ve had to struggle with over the last number of years and don’t have a solid answer.

    • EkoBuilt: the Evolution of the Home

      Hi Don – apologies for the delay in responding over the holidays.

      Thanks for your question, it makes me think of holistic sustainability, an approach that is best for “all worlds”.

      Two areas of focus will provide good guidance here:

      1. Use an insulation material with a high recycled/renewability content. Our installation of choice is cellulose because it uses recycled wood fibre so it is a material that has already sequestered carbon(in the forest) used as paper and therefore sequesters carbon a second time used as insulation. True, during the manufacturing process there is energy used but being a recycled/renewable based product more carbon is removed from the atmosphere than produced. The payback is instant. And, if use in a home with a high life cycle, it can indirectly remove more carbon from the atmosphere as most other homes use insulations that get produced with a lot of carbon (Rock wool, Fiberglass, Styrofoam).

      2. Build a type of home that will reduce the amount of energy used keeping with future climate targets for carbon reduction. Also a type of home with a high life cycle cost analysis.

      Our home of choice is Passive House. It comes with an incremental cost to build of 10% but reduces energy used 80 – 90% according to today’s building code. And with the savings in utility costs the incremental cost to build is instantly offset on a mortgage payment and therefore the pay back is instant.

      A home with a high life cycle cost analysis is one that is air-tight to 0.6 air changes per hour or less so that no condensation happens within the wall/roof cavity creating mould affecting the life of the home. Also a home that is built with low maintenance siding & roof materials with a 40-50 year warranty, as a little cash is required to keep the home maintained and more carbon offset as materials aren’t required to be replaced as often compared to homes built to code.

      Please let me know your comments on the above!

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