Older home on wooded lot
Energy Efficiency, Passive House facts, Passive House resources, 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.

Older home on wooded lot
Retrofitting Older Homes

Retrofitting an older home: taking a staged approach

Many of you have indicated that you’d like to hear from us about retrofitting older homes, and we love that idea too. We know not everyone is in the market for a brand new home!

There are a lot of good reasons to address the comfort and energy efficiency of an older home, particularly if you live in a neighbourhood that you love and don’t wish to leave. Staying in place and fixing what’s not working about your older home could be a really smart decision.

Much of our audience is in the Ottawa area, and a lot of great neighbourhoods full of older homes spring to mind.

So what to do when your home is many decades old, drafty and dependent on steep energy bills to keep it cool in summer and warm in winter?

Getting Started

You could start with the basement, if it’s a space of livable dimensions and not a cellar with a ceiling height too low for comfortable living. A basement, particularly in the mid-20th century bungalows found in many Ottawa neighbourhoods, can be a very smart place to start.

You could also work room by room or address a portion of your home, perhaps prioritizing the main living space or a home office / workspace. Prioritizing space that you occupy the most during waking hours will yield the biggest reward.

And frankly, it can be easier to tackle just a part of your home at a time if being out of your home for a long period and a much bigger, more costly renovation isn’t practical for you.

Key Components

If you can easily add insulation to the walls in your space, this will pay dividends, along with replacing exterior windows (and possibly exterior doors, if the room(s) involved have them) with much more energy efficient units.

The most important part of any energy conscious renovation/retrofit is the air-tightness. In the past we’ve written about the superb window and door options from Munster Joinery. These types of windows are three to four times more energy efficient than conventional ones and while they are extremely important, how they are installed matters just as much.

Hannoband multfunctional tape and window gasketUsing super energy efficient windows will only make a real difference if installed in a truly airtight manner. Conventional spray foam around windows will usually disintegrate less than five years after the initial installation, creating significant gaps that result in energy loss.

Passive windows should be installed with an expandable rigid foam gasket designed to be airtight and watertight for the life of the home. We like Hannoband, which can be sourced from various suppliers, including Small Planet Supply.

Radiant floor heating is a very popular and smart option for retrospectively addressing heating in your living space. Concrete, tile and engineered hardwood are all options for covering your radiant heating system.

Hydroshark radiant floor systemWe’re big fans of the HydroShark radiant floor heating system from Stiebel Eltron:

“HydroShark radiant floor panels are a professional, modular system designed to make radiant floor installation simple, reliable, and easy.

Everything you need to install is already mounted to the HydroShark panel.”

Get full details from the Stiebel Eltron website. And ask us!

For efficient air exchange in a newly sealed living space, we recommend Minotair’s HRV unit. This unit will effectively control temperature, ventilation and humidity in your space, making for a very comfortable and healthy home.

When this system is installed with an integrated air source heat pump designed for a passive house environment, it also will have the capacity to heat the home when outdoor temperatures drop as low as -5°C. In this scenario, a HydroShark radiant floor system would only need to handle heating for a few months each year, when the outdoor temperature falls below -5°C.

Read more information on Minotair from Quebec and their HRV units on their website: minotair.com.

Real Savings for Heating & Cooling

The best part of this combined systems is the cost. The HydroShark costs under $5,000 which is less than half that of a conventional radiant floor system. The HydroShark system will also result in a 90% reduction in actual energy consumed, making the system pay for itself very quickly.

A Minotair system will total less than $8,500 installed, which is on par with the cost of a conventional air-conditioning / HRV unit.  In addition, it also comes with 90% energy savings in a passive environment, making it exceptionally cost effective.

Retrofitting to PassiveHouse

In this series we’ll next look at what’s involved in a complete retrofit of an older home to passive house standard.

Got a sustainable home building topic you’d like to see explored here? Let us know!

Photo by Scott Webb on Unsplash