How Much Does a House Lose by Air Leakage

I had the privilege of teaching a Building Science lab at Humber College last year and the innovative things these students did even in light of a bleak job market impressed me. I received an email recently from one of the graduates, David Dokhoian, who sent me his energy modeling calculations to express the impact of air leakage on an average home. David’s graph says it all:

David's Calculations II

David Dokhoian’s done the number crunching on air-leakage for a typical new Ontario home. Yes, its true the energy losses are low through the envelope, but its readily apparent that taking care to air seal the house has significant energy and durability benefits.

Curiously, the Ontario Building Code doesn’t require any minimum air leakage or a simple quick test, which is just leaving money on the table. We’ve tested new townhomes (attached on both sides, should be air tight) and can be upwards of 6 Air Changes per Hour.  We get told often that we’re splitting hairs by making homes so air tight, but we respond two fold:

  1. If installing an HRV or ERV in the house, you should make that mechanical investment earn its keep. We do that by making the home more air tight, ideally less than 2 Air Changes per Hour. Installing an HRV in a leaky house costing the home owner more money and is borderline belligerent.
  2. Homes with high R-value enclosures that are indiscriminately air leaky are just begging for a recall and an eventual moisture related issue.

Don’t be sloppy, seal it up and ventilate the house mechanically!

Finally, a big thanks to David for crunching the numbers! Thanks for all your help on the double brick study too!


David Dokoian’s LinkedIn contact:




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New Passive Building Standards for North America

The new Passive Building Standard will be announced this fall at the Passive Buildings Conference in California and it will be a game changer. Currently, a steadily growing grass-roots movement is calling for more resilient housing and this will be the one unifying document that will trigger the much needed wave of popular support for high performance housing on this continent.

Smith House Illinois

Katrin Klingenberg of PHIUS has been making in-roads in the gritty North American political climate and it looks as though she will finally get a break. The modest house above was the first North American house to be certified by Germany as a PH. It is located in Urbana Illinois.

Many inspiring designs are emerging that bust the myth that beauty is a odds with efficiency and this new standard will only help to strengthen that point. For a full reading of why a new standard is being developed for the North American climate, read GBA’s Guest Blog this month.

We look forward to learning about it at the conference!


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How Much Lead is in your Toronto Water?

When it comes to lead, most scientist agree there is no “safe level”, but the cut off has been arbitrarily set at 10 parts lead to a billion parts of water (PPB) by Health Canada. The Toronto Star pulled together a great graphic and allows you to search your postal code to see how many tests failed in your neighbourhood and by how much.

In my neck-of-the-woods, a mere 14 water tests were done and just over 7% were above the 11PPB threshold.

If you drink tap water like we do, its a good idea to see where you’re lead levels are because once the lead gets in your body, its nearly impossible to get it out. As the EPA web site says “Infants and children who drink water containing lead in excess of the action level could experience delays in their physical or mental development. Children could show slight deficits in attention span and learning abilities. Adults who drink this water over many years could develop kidney problems or high blood pressure.


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Jamie Sarner’s Blog Post on Home Renovations

I met real estate agent Jamie Sarner recently at the Annette St. Library where BGG gave a talk on the intricacies of renovating vintage Toronto homes. Unbeknownst to me, Jamie was taking notes!

Its rare that real estate agents take an active interest in community and energy efficiency so I was so pleased to read Jamie’s excellent blog post on energy efficiency! Have a read:

How to Saver Energy and Reduce Your Bills

Thanks Jamie!



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Building the Ontario Cottage

Deciding to build a cottage in Ontario comes with many tough choices that can saddle the owner with onerous utility bills for generations to come when really, they simply want a reliable place that enriches family memories or to celebrate their golden years in comfort. Yet all too often, owners unwittingly get pigeon holed early in the design stage into installing complex mechanical systems that at first glance look like a good choice, but often prove to be very expensive to operate, maintain and install.

The current trend in designing cottages is for that modern look with lots of floor to ceiling windows that face the lake – even if the lake is north facing – and the wants list looks like this:

  • Modern look
  • Floor to ceiling windows facing the lake
  • Wood burning fireplace
  • Ground Source Heat Pump for heating & cooling

Thus begins a cascading series of decisions that can have a huge effect on how you’ll spend your money after the cottage is built. The second point throws a wrench in the works as windows don’t perform as well as insulated walls and when we replace insulated wall area with glass area that loses warmth far too quickly in winter and lets in lots of heat in summer and winter in some rooms; it challenges the mechanical system.

How’d We Get Here?

Which is why we take issue with the last point- its not the only way. Curiously, the Ontario Building Code will have a huge impact on the completed design if not reducing the window area below 22% of total wall area, then forcing the hand of the owner to go with Ground Source Heat Pumps (GSHP) if no natural gas lines pass on the street. And though a good GSHP works well for both heating and cooling, there are usually many shortcomings and one is that in really cold months, a GSHP system will use electric resistance heaters as a back-up system – which is the most expensive way to heat a house and only stands to get more expensive with time.

Heat pumps use electricity, but unlike electric resistance heaters that “burn” 1 unit of electricity to make 1 unit of heat, the magic of heat pumps is that the electricity doesn’t make heat – it moves heat. In fact, a heat pump moves heat so efficiently that 1 unit of electricity can make 3 -4 units of heat. In winter time, the GSHP moves or pumps heat from one place (outside) to another (inside) and in summer the heat is moved in the other direction.

Next is the crediting of efficiency in the eyes of the government approved software used by Certified Energy Auditors who do calculations on your cottage design as part of the permitting process if you have more than 22% window to wall ratio. The histrionics on this topic are interesting as electricity has always been seen as the more “green” option when compared to a fuel like natural gas, so that with energy modeling software, electrical systems will have a “better” EnerGuide performance score than other fuels that don’t rate as 100% efficient even though the electrical generation plant, transmission and its grid distribution systems are far from 100% efficient.

Are you Dissing Ground Source Heat Pumps?

It’s not that GSHPs are bad, it’s just that unlike a furnace which has a factory set efficiency, a GSHP is a unique piece of machinery with pumps that need to work with the fluctuating conditions outside and is designed by one person – who many not be an expert in GSHP design – yet is assembled by another technician who may beg to differ with the designer. Adding insult to injury, part of the system has to be installed in the great outdoors.

With part of the system buried underground, troubleshooting the bore field turns into a mind field. Compare that to a furnace pulled out of a box that’s just plugged into the gas line, fed electricity, connected to ductwork and barring some major design oversight, the system functions at the plate efficiency. Not so for GSHPs. It isn’t uncommon for new cottage owners to either put up with cold winters or be saddled with incredibly huge electricity bills during winter months and what if electricity prices go up?

Solution: Computer Energy Simulation for Optimised Building Shell

So is there a better way? Yes, invest in energy modeling early in the design phase. Often the designer, architect or builder will have to go through this process anyhow to pull a permit if you have more than 22% window to wall ratio and if you hire a company like BlueGreen Group which specialises in building shell optimization for efficiency, we can help you out of this trap often with imperceptibly small tweaks to the design.We can help lower the heating demand to the point where a GSHP can be either significantly reduced in size (less expensive bore field drilling!) or where alternative heating systems become more practical.

If you get the heating load low enough through good envelope design and attentive assembly, you may be able us use an Air Source Heat Pump (ASHP) which, much like a furnace, is pulled out of a box and its installed efficiency is close to its plate efficiency. In the last number of years the Asian manufacturers have made huge leaps in efficiency gains to the point where an ASHP runs more efficiently than a GSHP and is only 30% the installed cost of a GSHP.

As for the fireplace, Rumford style fireplaces should be avoided especially on outside walls because the massive masonry chimney can’t be insulated and getting a draft gong on a cold day is difficult. Best to situated it in the house where the chimney is kept warm, but to also consider installing an air tight stove or masonry heater which have all of the plus sides of a traditional fireplace and very few downsides. Besides who wants to spend time splitting and schlepping wood, we just want heat and fire!

Other tips include, buying land that sits to the north of the lake so you can have your cake  – large south facing windows for maximum view and winter solar heat gain – and eat it too. Next, consider installing Photo Voltaic electrical generating panels on your roof, that way if you opt for a the smaller ASHP, you can use the electricity generated on your roof. You can also use the roof top power generated to heat your water with a new air source heat pump water tank too.



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New Air Tightness Record in Ontario (Dare I say Canada?)

It happened again yesterday: a new record (tell me if you know of a tighter house in Ontario if not Canada!) for air tightness was broken in Oakville by Certified Passive House Consultant (CPHC) Ed Marion of Passive House Ontario.

And this was just a pre-drywall test, so it can only get better from here.

Ed atop the Canadian record!

Builder Ed Marion atop the new Ontario record holder for most air tight home! Forget the fact that the house has the greatest attention to detail for long-term durability; this attic has a walk way replete with electric lights and yes an electrical outlet in the attic! Talk about attention to detail!

And to think that only in November of last year I was bragging that we’d tested “The Most Air Tight [Off Grid] House in Ontario!” and now, though this house isn’t Off-Grid, its the most air tight we’ve ever had the pleasure of testing.

You’ll recall the last record air tight house built by Dennison Homes came in at 0.52 Air Changes per Hour at 50  Pascals (ACH50) with an Equivalent Leakage Area (ELA) of 32 square inches. For the record, the Passive House Institute in Germany requires that all Certified homes have no more than 0.6 ACH50, so these two Ontario-built homes beat the requirement by a country mile. And now, as of Cinco de Mayo 2014, Mr. Marion’s build takes the top prize with and ACH50 of merely 0.29 and ELA of 13.3 square inches. That’s right, Mr. Marion beat the German air leakage requirements by over 50%!

Builder Ed Marion

Builder Ed Marion showing the double wall assembly detail of the new build going up in Oakville Ontario. Yes it was a brutal winter, but the taping went on and it sure paid off in air tightness results. With most of the house insulated using cellulose (installed by the specialists at GreenSaver) the vapour open building assembly will produce a durable and very comfortable new home.

To put the air leakage into perspective, many new homes are so willy-nilly on air tightness (there’s no minimum air leakage in the Ontario Building Code and most new homes are NOT tested for air leakage – which is a real shame given the increased durability, comfort and reduced call-backs when you ensure the house is more air tight… but I digress! ) that you could ride an upright bike through the cumulative hole, but this house, you’d have a hard time passing a small Timmy’s double-double through it. Might have to use a straw come to think of it…

Congrats Ed, we’re very honoured to be able to work on your builds, it was impressive watching it come together these past few months.

As for the rest of you, if you can find me a 3rd party tested home in Ontario – make that Canada – that’s more air tight (less than ELA 13.3 than this, I’ll eat crow, blog about it and I’ll buy you a large double double and supply the straw so you can drink it! But until then, I will assume this is the most air tight house in Ontario if not in Canada.



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Passive House Porn Production!

I didn’t think there was much going on in sleepy Canada in the way of Passive House buildings, but boy was I wrong! Finally, a hard covered book replete with gorgeous centerfold spreads of some of the most beautiful homes this country has to offer – who knew efficiency could be so sexy and Canadian!

Toronto architect Terrell Wong has put together a beautiful coffee table book called Passive Buildings in Canada and is available from Blurb now!

Terrell’s book highlights a few of the [near] Passive Buildings and gives a cross sectional diagram for all the techies out there looking for a better thermal enclosure system. This book is truly a celebration of what’s happening now in Canada and is a must read & visual feast for anyone pushing the envelope on performance!

Pull out your credit card and order this book. This PH-porn comes by snail mail in a discrete brown envelope so no one will suspect your little indulgence!

Congrats Terrel thanks for the fine work, you deserve to make a fortune on this book and we look forward to the next one!

Passive Buildings in Canada

BGG had the pleasure of testing a number of the homes highlighted in this lovely book; chief among them the mellifluous rammed earth home constructed by Aerecura.

Passive Buildings in Canada ii

The book is a fine balance between bold glossy pictures, stats to turn on the low energy enthusiast and crisp illustrations of wall cross sections with enough detail to make you think your could build one yourself!

… and you thought you knew what PHPP stood for… Buy this book! Now!


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BGG covers OHBA PM Course in Eastern Ontario

BGG was in Ottawa last week delivering the OHBA’s Project Management course in a one day workshop held at the Greater Ottawa Home Builders’ Association.


BGG working with builders in eastern Ontario.

BGG delivers another workshop to builders in eastern Ontario. From Left to right: Back row – Greg Labbe, Rob Blommestyn, Brandon Joyce, Blair Joyce, Shane Ottens, Tim Howlett, Michael Hlohinec and seated – Chelsea Baker, Bruce McNulty, Ken Dantzer.

Thanks to the builders that participated, I learned much from you too!


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What Makes HARDCORE Hardcore?


When you see good work, it makes you feel better about the state of things and in this short clip produced by the gents at Hardcore Renos, we talk about the points that matter to us!

Good work Gents!


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Does the Homeowner Know You’re a Blowerdoor Virgin?

When setting out to build an efficient house, the elephant in the room is air tightness. Industry is resisting mandated air tightness testing if thresholds are introduced meanwhile building codes are ratcheting up efficiency on all fronts except air tightness. Having debunked the myth that “a house needs to breath” its becoming painfully obvious to any building scientist that the lowest hanging fruit on the efficiency tree isn’t geothermal but simply producing a more air tight home. You’ll have to do it eventually, why wait and make homeowners pay more for heating and cooling their homes? Not testing your builds just reflects badly on you and your reputation.

Shervin congratulates Ed Marion on shattering his air tightness target.

No stranger to regular air tightness tests pre or post occupancy, Ed Marion shatters his air tightness target and is being congratulated by Shervin…again.

Our field testing on new homes show that even new homes can be super leaky, in fact as much as 7 Air Changes Per Hour at 50Pascals*. To put that air leakage rate in perspective, the sum of heat lost in winter and summer humidity let in by air leakage will be greater than the energy lost through the entire wall surface area. It begs the question, why spend more on an iota of wall insulation when the house is so leaky? Adding insult to injury these homes typically all have Heat Recovery Ventilators installed and this device requires an air tight house to earn its keep.

Don’t be scared…

The heart of the matter lies with potentially “failing” to make the air tightness threshold and what that might mean to scheduling issues in production or profit loses that might occur, but in our experience, the fears are overblown. The costs are negligible if the testing is done at the right time, beside once a builder sees where the leakage takes place, they typically don’t make the same mistake twice. This brings us to the crux of this blog; if you could invest in only one air tightness test; pre-drywall or pre-occupancy which would be more crucial?

Hands down, the pre-drywall test is the best stage to have your house tested so that a) you can adjust what you’re doing on future builds and b) you can remedy the problem. In our experience, repairing air leaks before the drywall is up usually stacks up to less than a half day of labour and less than $50 in airsealing materials. That’s low cost and low risk for significant benefits like reduced call-backs and the potential for situations like an “ice dam” or mould in the attic or humidity driving into the envelope.

“What could possibly co wrong?” A pre-drywall blower door test would have saved this homeowner $10G to fix the problem. The above clip isn’t from a roof leaking rain, this is condensation. In this 3rd floor attic of a $1.7million house built in 2013, ‘Stack Effect’ drives moist conditioned indoor air up through pot lights and a pocket door and into the cold attic. The moist air condenses on the aluminum of the roof vent and drips on the attic floor and into the master-bedroom ceiling. Note municipal inspectors check to see if the house meets the minimum standard; they don’t check for air leakage and don’t assume that spray foam gives you immunity either.


Everything is pointing to higher efficiency and to build a house that’s leaky is just too much of a risk. The next code cycle are going to raise the bare on envelope R-values and mechanical efficiencies not to mention the fact that the way we calculate heat loss (F280) in buildings starting in 2017 will include the option reduce the air leakage rate from 4.8 to the lower leakage rate you plan to build your house to**!

Here’s the pitch…

So here’s the pitch, bring us out to do a pre-drywall air tightness test on your next project, mention this article and get $100 off your first test***. This is a no risk offer that will allow you to see how your builds stack up and give you a glimpse of what high performance builders routinely before and after drywall.

If you’re new to blower door testing, you couldn’t ask for a more caring partner than BGG!


*The homes in question were tract-built, town homes being built in 2013 in Brampton slated to be ENERGY STAR® which has a maximum of 2 ACH50. Stunningly, most of the air leakage was from the garage – think carbon monoxide in the living room. Let’s just say, it’s a good thing they investing in pre-drywall blower door tests so that they could remedy the air leakage in order to make the ENERGY STAR® grade. 7 air changes per hour puts this house with a weatherised 1920 uninsulated house.

** For perspective, we’ve tested new homes with air leakage rates lower than 0.5 ACH50 and renovations of 50 year old homes to less than 0.6 ACH50 and 100 year-old brick homes to less than 2.0 ACH50.

*** Offer valid if booked before June 1, 2014 and may be subject to geographic restrictions, call for details.

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