Sustainable New Construction 2016

Sustainable building class

An unparalleled learning experience!

Be a team member in the construction of a remarkable sustainable building, from foundation to finishes. Endeavour’s full-time, immersion program puts you front-and-centre as you work with faculty members on an innovative building using natural and low-impact materials to create a super-efficient, healthy, affordable building.

Click here for 2016 course & project details…


Repairing Clay Plaster (with toilet paper?…)

Earthen plaster repairs

Questions concerning the durability of clay plaster – especially as an exterior plaster, and even more especially in cold and wet northern climates – get raised any time we suggest using clay plaster to a client. We recently had the experience of returning to the first building we clay plastered, back in 1994. What we saw and learned greatly increases our confidence in the use of clay plasters!

What do we mean by “durable?”
When we talk about durability, what do we really mean? Let’s say we’re comparing two kinds of exterior siding: clay plaster and vinyl siding. Intuitively, we’d probably say that the vinyl siding is more durable. But scratch the surface a bit… no material is indestructible, so what we really mean is “how long before it needs fixing or replacing.” Vinyl siding can last quite a long time before it wears out or breaks. But it does wear out and break, and when it does what can be done? Typically, nothing. It gets removed, taken to landfill, and replaced with new material.

The clay plaster may be more susceptible to wear (especially if it’s placed too close to the ground, as we’ll soon see!). But when it is damaged, it can be easily repaired at almost no cost and made as good as new, with no landfilling and no need for replacement.

Using Clay Properly
The first step in making clay plaster durable is to plan properly. The worst section of damage on this 12 year old home was next to the utility door on the north side. The building is way too close to grade… we recommend 8-12 inches minimum, but didn’t do that here. It was also unprotected by a roof overhang… despite the whole building have wide overhangs, this northern corner protrudes out to be almost in-line with the roof. Two strikes! And yet, here in the worst possible scenario – with rain hitting it, snow piling against it and no sun striking it to help dry it out – the plaster was still intact and still protecting the bales, it just didn’t look pretty anymore. Other places on this building saw some cracking, a result of not using enough fiber in the mix. Our clay plasters have for years now featured high quantities of fiber and we’ve avoided these kinds of cracks.

Getting the repairs going
We addressed the two areas that had seen a fair bit of erosion with new clay plaster. But clay plaster mix is terrible for filling cracks… the large aggregate and high fiber content that make for great plaster also makes for a mix that does not want to be pushed into long, narrow cracks.

Even though we opened up all the cracks with a pallet knife, the openings were nowhere near the size needed to push in an actual plaster mix. In fact, a mix with almost any aggregate (sand) in it does a lousy job. Even if it fills the crack adequately, there is always sandy mix left on the surface of the plaster calling attention to the repair forever after. And if we used straight clay, the shrinkage would be extreme and there would be micro-cracking along the crack.

Toilet paper to the rescue!
As we contemplated how to make a mix that would adhere to the existing clay, but would have such a fine aggregate that it could be wiped off the surface, we started to think about cellulose… little paper fibers that would be very fine but still add a lot of strength to the repair mix.

Earthen plaster repairs

Toilet paper provided the cellulose fiber we needed, and mixed in the blender with clay (and a bit of talc) created a smooth mix!

We came up with a highly scientific formula: 6 arm-spans of toilet paper (two-ply) to 2 cups of clay, with a bit of talc powder and water to the desired consistency. What we got was a sticky mix that was easy to work into cracks, that bonded well with the existing clay, didn’t shrink at all and was very easy to work with!

We were able to fill all the cracks to their full depth using a putty knife and pulling back and forth across the crack until it wouldn’t accept any more material. Then one pass with the putty knife left the surface scraped back cleanly to the original plaster.

Low impact repairs… like, really low impact!
The materials we needed to do all the repair work were right on site. The clay that had been leftover from the initial plastering in 2004 was left in a small mound near the house. Slowly, that mound became a “garden” of sorts. We were able to shovel clay from the back side of the pile and leave the garden undisturbed. Some natural pigment, some sand (and some TP in the cracks)… that’s all that was required.

I don’t think we could even calculate a carbon footprint or embodied energy for these repairs!

Mixing and applying a new clay paint
The largest area of the house had a red clay paint applied 12 years ago. There were enough cracks and repairs on this section that we decided to re-coat it with a coarse clay paint. We mixed 20 parts of the site clay with 10 parts of fine sand and 3 parts of pigment, and applied this runny mix using a sponge float.

A wetter mix with only 3 parts of fine sand was brushed onto the narrower bands of colour at the top of the wall. It was easy to cut a smooth line with this paint, making for crisp lines between the colour bands.

Fast work, faster next time
There were enough areas that needed attention on this house that we decided to completely re-paint the whole building. From first arrival at the site to colour matching the mixes to application and final clean-up, we spent a total of 3 days for 2 people (about 42 hours) on these repairs.
When this plaster needs work again in the future, there will be a paint mix in all three colours ready to be re-hydrated and applied. And since the colours match, spot repairs can be done instead of a whole new coat. If we’d been smart enough to do this the first time around, we could have cut the time for the job in half! We don’t expect cracks to re-open again, as no new cracks opened up on the building after the first couple of years.

A final layer of protection
One of the reasons we feel this clay plaster held up so well – despite being a less than ideal mix placed too close to the ground – was the inclusion of a top-coat of Primasil, a silicate paint primer from PermaTint.

Though it isn’t intended to be used as a “clear coat” finish, we have applied it this way on several buildings and it has done a great job of protecting the plaster from water damage while remaining highly permeable. In the future we will experiment with adding PrimaSil to our finish plasters and clay paints instead of water and see if building the silicate right into the material has a positive effect.

An endlessly repairable finish
The beauty of clay plaster is its ability to be maintained and repaired indefinitely. We had no waste from these repairs other than some sand and clay on the ground, and we had no expense other than a bit of pigment and a roll of toilet paper. And the pigment will be suitable for about a century’s worth of repairs of this extent! Now the plaster is once again gorgeous to look at and ready to handle another decade or two of keeping out the elements… Try doing that with vinyl (or anything else!).

The (Carbon) Elephant in the Room

There is an elephant in the room when it comes to our buildings, and it’s a carbon elephant… Every time we make or renovate a building, there is a carbon footprint as a result of the harvesting and manufacturing of the materials as well as the transportation involved. If we think this carbon footprint is negligible, we’re ignoring the elephant in the room!

Embodied carbon versus operational carbon
For many years, green building advocates maintained that the embodied carbon of building materials was not as important as reducing the operational energy use and carbon footprint. By this reasoning, it was justifiable to use materials with a high carbon footprint because they would eventually “pay back” that carbon “investment” with reduced energy use over time.

It’s not a trade-off
However, it is possible to make buildings with low-carbon building materials that match the energy efficiency performance of buildings that use high-carbon solutions. It’s a win-win solution… but it takes some adjustments to our way of thinking about buildings.

The carbon elephant
A comparison of the carbon footprint of a few different types of building shows that there can be a huge difference based on just a few material selections.


Carbon emissions of various construction types (from Making Better Buildings)


This chart shows the same 1,000 square foot house (based on the model house in the book Making Better Buildings). The two conventional approaches differ only on the choice of exterior cladding, one brick and the other vinyl siding. They have a carbon footprint many times larger than a best practice home made from low-carbon materials. But surprisingly, the straw bale home using lime-cement plaster actually has a carbon footprint slightly higher than a conventional home with vinyl siding. The same bale home plastered with clay has a dramatically lower carbon footprint.

Carbon sequestration
The carbon footprint numbers shown in the chart assign a carbon footprint to the cellulose materials (wood, straw, cellulose insulation), but don’t take into account the carbon sequestration effect of bundling a lot of carbon-based material into a building for a long period of time. There are conflicting notions of how to account for this, but at the very least there seems to be agreement that the sequestration completely offsets the carbon footprint. There is some reasonable argument to be made that these materials can actually have the effect of negating some of the building’s carbon footprint… that is, create a negative amount on the building’s leger. Things look different when this is taken into account!

Carbon emission footprint with sequestration of cellulose material at 25% of material weight

Carbon emission footprint with sequestration of cellulose material at 25% of material weight

By eliminating the carbon footprint for cellulosic materials and giving a sequestration factor of 25% of the total material weight, the carbon footprint can actually be put into the negative. However, those striving for carbon neutrality must remember that sequestration relies on the growth of new bio-mass to absorb CO2… we need to plant trees to replace those we’ve used in order to ensure these figures.

Carbon footprint as demonstrated by the number of carbon elephants emitted

Carbon footprint as demonstrated by the number of carbon elephants emitted

Different approaches not equal
The world needs carbon reductions immediately. Ensuring high carbon output today with the hope of a long-term reduction is a questionable strategy; it’s better to bank on getting our carbon footprint reduced now, especially if we can do so without sacrificing future reductions in the form of energy efficiency. When we start building very efficient buildings, the carbon footprint of the materials can start to equal many years of operating energy.

Carbon footprint by embodied carbon, 1 year and 10 year operational carbon for three climate zones

Carbon footprint of a foam-home, a high performance low carbon home and an older home, by embodied carbon, 1 year and 10 year operational carbon for three climate zones

This graph shows the embodied carbon of a high performance building using foam insulation, a best-practice low-carbon building and a largely un-insulated low-carbon building in different climate zones. Note that with best practice, there can be almost 10 years of operating energy before the building has the carbon footprint of a foam-based high performance house. And that’s without taking any sequestration into account! Obviously, we want to avoid the huge footprint of poorly insulated buildings, but ideally we want to do so in a low-carbon way. If we can build a low carbon home and use it for 7-8 years before we have the carbon footprint of a foam home, this is the option we should pursue!

No small effect
There were over 2.2 million new homes built in Canada in 2014. Using conventional materials, these homes account for 22.1 megatons of CO2 output. Using best low-carbon building practices can eliminate that altogether, and could even contribute 1.48 megatons of sequestration… almost 24 megatons of CO2 reduction!

Canada’s commitments under the Copenhagen Accord call for us to reduce about 127 megatons of CO2 given 2013 output figures. A move to building carbon-conscious homes could get us almost 1/5th of that target, in one industry, with little need for re-tooling or re-training of trades AND using materials that are harvested and produced in Canada. As a bonus, such homes are not necessarily any more expensive or difficult to build.

Kind of puts a positive spin on things, no?

For Sale: House that Makes an Income!

As followers of this blog will know, we at Endeavour have spent a lot of time on our Canada’s Greenest Home project. Our goal was to make the greenest home possible on an urban infill lot in Peterborough, and then to sell it on the open market to show that there is an appetite for “deep green” amongst home buyers.

The final phase of the project is now underway, with the house going on the market this week. Here is the Listing for 136-1/2 James Street.

The most interesting part of selling this home is how to put forward the unique value proposition we are attempting to make. Most home buyers look within a set price range for their new home, and do this with an implicit understanding that they will be assuming utility costs (heat, electricity, water) that are within a similar range to all other homes. This house radically alters that outlook: There are no utility costs and the home provides an income.

Energy production vs Use

Energy production vs Use

This means that the higher up front cost of buying a super-insulated and completely non-toxic home (LEED Platinum certified) has a very compelling overall financial picture. The solar income from the house averages about $3300 annually. The annual utility costs are around $1800 or $150/month (inclusive of heat, electricity and water, plus services charges and delivery fees). This means that for the remaining 18 years of the Micro-FIT contract, there is a $1500 annual income from the home after all utility costs have been covered!

Considering that an average home of a similar size in Peterborough will have total utilities bills in the $250-600/month range (from census data, 2011), this means that there will be an annual savings of $3,000-8,700 for this homeowner. Putting that extra money against the mortgage for the home can result in the mortgage being paid off 5-6 years earlier. And all that while enjoying a healthy and efficient home.

Mortgage calculator

Mortgage calculator

But can this case be made effectively in the current real estate market? There is no way to show this information in a quick and easy-to-digest form… the listing for the house shows the asking price, and a curious buyer would have to read the listing and inquire about more details in order to learn the whole story.

We hope that there are buyers out there who will be interested enough to find out the details. And we also hope that this helps to set a precedent for builders who want to make healthy houses that earn money and real estate agents who want to sell this kind of home!

If you’d like to help us set this precedent, please share this listing with your networks.

Touring Sustainable Homes

On October 3 and 4, two great organizations are teaming up to help get you inside some unique sustainable homes in Ontario!

The Ontario Sustainable Energy Association (OSEA) has its Doors Open event on October 3. On this tour, you can see a wide range of homes that employ a variety of renewable energy strategies, from solar electric and solar thermal to small scale wind and micro hydro.

The Ontario Natural Building Coalition (ONBC) has its Natural Building Tour on October 4. On this tour, you can see homes built with all kinds of natural materials, including straw bale, hempcrete, rammed earth, cob and compressed earth blocks.

The links above will take you to maps that show all of the homes involved in the tours. There will be no better opportunity to see and experience such a wide range of homes, and to learn all of the insights gained by the owners and builders as they created their projects.

What Makes a Building Product “Green”?

The Green Glut
The past 10 years have seen an explosion of building products being marketed to designers and builders as “green.” As the immense impacts buildings have on our planet’s ecosystem started to become clear to the mainstream building industry, marketing departments went crazy to identify just about every kind of product as being “green” in some way or another.



From my position as someone advising people on green building options, this “glut of green” causes a lot of confusion. If every product is green, what does it mean to really be green?

Real Green Criteria
In order for a product to meet Endeavour’s standard for green, it has to meet several criteria:

  • Must have low ecosystem impacts in the harvesting and production of the product. This includes considering both how and where the raw materials are extracted and handled, and what kinds of pollution/emissions happen during the production processes.
  • Must have low embodied energy and carbon footprint. This means understanding how much (and what kind) of energy is used to harvest and process the product and the size of the fuel and carbon footprint.
  • If applicable, the product must positively impact the long-term energy efficiency and/or performance of the building.
  • Should not use and definitely must not emit any dangerous chemicals or off gassing, during manufacturing, use in the home, or at end-of-life.
  • Must be durable, and have a reasonable end-of-life strategy (ie, where does it go when it’s taken out of the building).
  • Upcycled, recycled and re-purposed materials are preferable.
  • Local production is preferable to long-distance shipping.

Meeting Just One Criteria = Not Good Enough
Many building products are sold as “green” if they meet any one of those criteria. Unfortunately, the majority of building products sold as “green” fail (often miserably) when examined against all of these criteria. While the sales team will glowing focus on any glimmering of green in one category, rarely does anything with the green label come close to satisfying a full range of ecological criteria.

Living Products Expo

Living Products Expo

A Materials Revolution?
The dichotomy between products posing as green and those that are truly green was on display at the recent Living Products Expo, which I attended in Pittsburgh last week. Organized by the International Living Future Institute, the event was billed as “Inspiring a Materials Revolution.” And kudos to the organizers, because this really was the intention of the event.

What Makes Foam Green?
But at one point I found myself in a session that featured several product manufacturers presenting on their new green products. One was a rep from Johns Manville presenting a new polyisocyanurate foam insulation product that does not have added fire retardants (called Energy 3.E). Now this is an interesting achievement, since the flame retardants used in foam insulation are among some of the worst and most persistent chemicals in use on the planet, and up to 15-20% of flame retardant by weight is used in foams. The San Antonio Statement on Brominated and Chlorinated Flame Retardants should be enough to scare all of us away from using any products that use these flame retardants, so to have a foam insulation that eliminates them from its chemistry (without using questionable substitution) can be viewed as a major step, one worthy of the label “green.”

Johns Manville foamExcept that if we put even this insulation to the test of our criteria list, it still fails on many counts. The foam is still a petro-chemical product, and if we don’t like what the oil industry does to the planet (from exploration impacts to drilling sea beds or excavating tar sands to the vast amounts of energy consumed and carbon produced to spills and “toxic events”) then it’s hard to see any foam product as being green. Foam insulation has very high embodied energy and carbon output. It still uses questionable chemistry, has no end-of-life plan and is shipped long distances from a centralized factory. Energy 3.E might be “greener” than other foams, but I don’t think it can really be called green or sustainable. This despite the fact that the product has won all kinds of green awards and has been widely celebrated.

Ecovative mushroom foamReal Green Insulation
This point was driven home by the next presenter at the same session, this time from Ecovative Design. This company has developed “mushroom foam,” a material that is made from mycelium (mushroom roots) grown amongst agricultural waste fibers. Among its many uses, it can be made into an insulation product with very similar performance qualities as plastic foam. This material satisfies all of the stringent criteria we apply to products in our buildings, and it is naturally flame resistant (interestingly, it turns out that the phosphorus atom the Johns Manville scientists managed to insert into their foam occurs naturally in the mycelium). Unfortunately, Ecovative’s insulation products have not yet reached the mass market, while the foam product has. But the stark difference between the two is a perfect illustration of the difference between being “sort of green” and “really green.”Ecovative process

At the same conference, I gained a more in-depth understanding of two programs that are intended to help builders tell the difference between real green products and those that are just pretending to be green.

Cradle to Cradle products programCradle to Cradle Certification
The Cradle to Cradle Products Innovation Institute certifies products on a scale from “bronze” to “gold” based on their satisfaction of a wide-ranging set of criteria. The C2C Products Registry allows one to select a product category (such as Building Supply and Materials) and find products that have met their very high standards. I highly recommend this when searching for truly green products to use in buildings, though the overall number of products is still relatively small.

declare labelThe Declare Label
Declare is a labelling system introduced by the Int’l Living Future Institute. The Declare label is billed as “a nutrition label for the building industry.” It focuses largely on a transparent declaration of all the ingredients in a product, and where those individual components come from. The Living Building Challenge building certification program has a “red list” of chemicals that it does not allow to be in a building. This label is a means of finding out if a product contains a red list chemical, and what things it contains that may not be desirable even if it is not on the red list. Declare does not consider ecosystem impacts, carbon emissions or other elements of manufacturing, and so is not quite as comprehensive as Cradle To Cradle, but it is still a great development and a useful tool for builders looking at green in a deeper way.

Green Chemistry and Local & Natural
green chemistry principlesAs stated in the Living Product Expo’s desire to spark a “materials revolution,” there is a real move happening toward creating and using building systems that are truly better for the planet. John Warner, a founder of the “green chemistry movement” was a speaker at the Expo, and more and more material developers are starting to use the principles of green chemistry for the built environment. Having presented to the Expo about Endeavour’s methods for prefabricating straw bale wall panels, I found it interesting that the most promising sustainable building systems are relatively low-tech, use waste streams from other processes and are simple to replicate in smaller, regional “micro-factories.” Mushroom foam, straw bale walls, cellulose insulation and so many other effective, truly green materials don’t require major industrial apparatus. To a large degree, this is what makes them truly green. Keeping it simple, local and natural is often the best way to ensure it’s green!

Circle Organic Farm Tour

In 2013, Endeavour’s Sustainable New Construction program undertook the building of a large farm building for Circle Organic Farm in Millbrook, Ontario.

The building included a 1,500 square foot vegetable processing area on the main floor (built with straw bale construction) and another 1,500 square feet of living area for farm workers and a farm office on the second floor (built with double stud framing and cellulose insulation). Adjoining this building is a 2,000 square foot buried root cellar. This root cellar was recently featured in a Trent University study about low-energy root cellar systems.

The building is now in its second year of use as the hub of operations at the busy farm, and is settling into the landscape comfortably.


Product Review: Allback Linseed Stain Wax

linseed oil wax review

At Endeavour, we are kind of obsessed with finding good-quality, non-toxic finishes for common household surfaces. Many homes have a lot of wood surfaces, and it can be particularly difficult to find non-toxic finishes for wood.

Allback is a Swedish company that specializes in making organic linseed oil paint products. We’ve used numerous of their products, purchased in Canada from Solvent-Free Paint. For a recent shelving project, we decided to try the Allback Linseed Oil Wax.

This product contains organic linseed oil and natural beeswax mixed with a variety of different pigment colours. We chose the white colour, but there are about 8 colour options in this product line.

Application is very simple. The oil-wax is rubbed onto the surface of the wood, allowed to sit for at least 30 minutes, and then rubbed back with a lint-free cloth. In the end, we used a buffing pad on an electric polisher to do the rubbing back, as this also buffs the wax to a nice finish. That’s it! One coat, and the wood is well-protected, with a bit of wood grain showing through.

We were very happy with the quality of the finish, and within 24 hours water will bead on the surface and typical kitchen stains wipe off without leaving a mark.

The product comes in a 7 ounce jar for $15 (one jar did our entire project with some left over), or a 1 liter pail for $59.

This is a wood finish that we would highly recommend!

Why We Love Earthen Floors

earthen floor clay floor how-to

Take one step – especially with bare feet – on an earthen floor and chances are you will be sold on the idea. You will want an earthen floor of your own. And not only will you be making happy feet when you choose an earthen floor, you’ll be making one of the most radical-yet-simple sustainable building choices… one that could dramatically reduce the environmental impacts of the built environment in a meaningful way.

earthen floor workshop and how-to

Clay, sand, fiber… that’s it!

A true game-changer
With the construction industry touting just about every option as being “eco-friendly” these days, it can be hard to know what choices really do make a difference. Earthen floors are a truly eco-friendly option. Using just four basic, natural, chemical-free and abundant materials that are minimally processed on site, an earthen floor creates a durable, healthy finished floor with the lowest possible environmental impacts. Mix the right proportions of clay, sand, natural fibers and drying oils and you’ll have a floor that is as beautiful as it is planet-friendly. The embodied energy of a 3/4″ thick earthen floor is 0.16 MJ/square foot, a tiny fraction compared to 3 MJ/square foot for hardwood, linoleum and concrete flooring of the same thickness, and 10-25 MJ/square foot for tile.

Really, a dirt floor?
It is often difficult for anybody in the “developed” world to consider an earthen floor as part of a clean, modern home. But earthen floors can be the visual showpiece of a home. A well-made earthen floor is a thing of beauty, bringing a texture and visual impact that cannot be replicated with any other material. Natural clay colours or natural pigments offer a wide palette, and a variety of fiber options can be used to great effect. And then there are the oil finishes which can add a rich lustre and additional colour options.

Are hearten floors durable?
Earthen floors are not a common option, and therefore most people do not have experience with seeing an earthen floor wear over time. In fact, these floors have very similar wear characteristics as most other natural floor materials like wood, bamboo and linoleum. All of these floor types can have a long lifespan under typical use conditions, although all are susceptible to scratching and gouging if mistreated, and all will require occasional refinishing to protect and enhance the surface of the material. Earthen floors are no different, and are quite easy to repair and refinish should some damage occur. I witnessed the earthen floor at Arts Centre Hastings spend a night under water after a large cooler full of melted ice broke, and yet after mopping up the spill the floor was not affected at all!

Place them wisely in the building
Though durable, it is wise to place them appropriately. Entryways, especially those that will see a lot of salt from snowy boots, can stress an earthen floor. Areas which will see a lot of dragging of chairs and furniture may not be appropriate. But if the use of the floor is for interior foot traffic, they hold up very well.

How does it work?
The clay/sand/fiber mix of an earthen floor may not seem like an ideal combination in a heavy-wearing scenario like a floor. These elements combine to make a substrate that can be easily packed and levelled. A typical earthen floor mix is 1 part of clay, 4 parts of sand, and 1 part of finely chopped fiber. As clays and clay soils can have different properties, it is always good to experiment with new materials before pouring an entire floor. Once this mix has been poured and troweled level, it is allowed to dry. Then the real magic occurs: several coats (anywhere from 2-6) of natural oil finish is applied to the floor. The oil penetrates into the clay/sand mixture and hardens around it, creating a tight and water-resistant finish that is very durable. The process is similar to natural linoleum, where linseed oil is mixed with sawdust. As with linoleum, the result is surprisingly solid.

Where can an earthen floor be used?
Earthen floors can be laid over many typical floor bases, including concrete slabs and plywood sub-floors. As

earthen floor clay floor how-to

A living room with a wood stove is a great place for an earthen floor

long as the floor base is stable and doesn’t have excessive flex or deflection, then an earthen floor can be laid. Typical thickness for a finished earthen floor is 3/4″, though it is possible to make them thicker. The floors can be laid over hydronic heating tubes, or used under wood stoves or other sources of heat. Simple substrate preparations are used if the base is either very smooth and shiny or if it is water absorbent.

It’s easy to learn to make an earthen floor
The steps involved in mixing, laying and finishing an earthen floor are very straightforward. If you think an earthen floor might be in your future, you can check out our upcoming earthen floor workshop, where you’ll get a chance to mix, pour, level and finish a complete earthen floor.

Getting Rid of Radon

Radon remediation

Those of you who follow Endeavour’s work will know that we take indoor environment quality very seriously. Every material that comes into one of our buildings is carefully vetted for its chemical content, and all of our finishes are chosen to be non-toxic. We pride ourselves on making buildings that have the best possible indoor air and water quality for the occupants. This is an aspect of sustainable building that is all too often forgotten, or given minor consideration via the use of low-VOC paints or other small steps.

Radon concentrations in Southern Ontario

We have long been aware of the issue of radon gas; the presence of radon gas is an important consideration when trying to create excellent indoor environment quality. Health Canada says: “Radon is a colorless, odorless and tasteless gas formed by the natural breakdown of uranium in soil, rocks and water. It seeps from the ground, and small amounts of radon are always present in the air. If radon gas enters a closed space like a home, it can build to higher concentrations. Radon is radioactive, and potentially carcinogenic if enough of the gas builds up. It is estimated that radon exposure is responsible for about 10 per cent of lung cancer cases in Canada, second only to smoking. Health Canada estimates that 1,900 Canadians died in 2006 from lung cancer resulting from radon exposure.”

Radon measurement table

Table from

When building our Canada’s Greenest Home project, we certainly considered the issue of radon, but after consulting some radon concentration maps and the Peterborough City-County Health Unit’s radon measurements in area homes, we didn’t think that radon would be an issue for this home. Especially considering the heavy duty vapour barrier and careful air sealing we knew we’d be doing, we thought the risk was extremely low.

However, a radon test of the basement – an integral part of getting our LEED Platinum certification – showed that we had very high levels. A long term (3-month) test gave results of 485 Bq/m3 (Becquerel per cubic metre), well above the Canadian acceptable limit of 200 Bq/m3, which itself is above the World Health Organization‘s recommended limit of 100 Bq/m3.

Despite the dangers of long-term exposure to radon gas, it is not so difficult to remedy a high reading, especially in a well-built home with a good basement.

We bought a testing device ($150) and an extraction fan ($250) from Radon Detect. The testing device can give short term (48 hour) and long term readings of radon levels. When we first plugged it in, we had readings in the 370 Bq/m3 range.

The process for lowering the radon level is to drill a hole in the basement slab to extend a 4-inch pipe down into the gravel below. This pipe is then directed out of the building through the basement wall to exhaust outside. We chose to use a fan mounted outdoors, but there are indoor options as well.

Our readings on the meter dropped by over 100 Bq/m3 to 223 Bq/m3 by just installing the 4-inch pipe, prior to hooking the fan up to the power source! Within 48 hours of turning on the fan, the meter was reading just 5 Bq/m3, well below any level of concern.

What is of concern, however, is that all the available information indicated to us that the Peterborough area is considered quite safe from radon, with the Health Unit reporting that only 8% of homes tested higher than 200 Bq/m3. However, the operator of Radon Detect told us that every home he’s ever seen tested in Peterborough has been higher than that, and certainly our readings were very high. Since radon comes from radioactive decomposition of rock and soil, this would indicated that at least our closest neighbours likely have high radon levels, and that high levels may exist in many more homes than we were led to believe. We were double the already-high allowable limit from Health Canada. At least now we own the testing equipment to help others see if they have high levels of radon.