The Exterior Walls

The exterior walls of the net zero ready house will be made from a double stud wall filled with blown in insulation. The double stud wall is basically two traditionally framed walls placed a few inches apart which create a space in between for an extra thick layer of insulation. The exterior wall of the double stud wall will be the load bearing wall and will be made from 2 x 6 studs spaced at 24 inches apart. The interior, non-load bearing wall will be constructed of 2 x 4 studs also spaced at 24 inches apart.

A vapour barrier and drywall are attached to the interior wall. House wrap and siding are attached to the exterior wall. In between the interior and exterior surfaces will be 12.5 inches of insulation, likely dense packed cellulose with an R value of 3.8 R/inch, giving the walls an R-value about 47.5.

The double stud wall seems to be the most cost effective way of achieving the desired high R value. Using other methods and materials, such as ICFs or SIPS, may have resulted in somewhat thinner walls but would have been much more expensive.

The frame for the house will likely be prefabricated in sections by a factory framing shop, then transported by truck and assembled at the build site. The Europeans have got this down to a super efficient, highly customizable, assembly line. Here's a video:



I'm not sure how it's done here in Toronto but we'll find out soon enough.

Goodbye garage

Word is from someone on the PAL review panel that the inverted slope driveway on the original plans is not going to get approval. Toronto is apparently trying to discourage this type of driveway because of potential drainage problems (an inverted slope driveway guides water towards the house leading to possible flooding problems if drainage is not carefully installed and maintained) but regardless, in this case, the slope of the driveway would have been too steep anyway.

The driveway/garage, then, has been replaced with a full basement and a parking pad.

Some other minor changes from the original include front window layout and backyard wall/patio layout.

One concern with the new front window area is the increased amount of summer heat it will allow into the house. Some type of exterior shading device will have to be built to prevent overheating.

The Basement

The last post discussed the three main requirements for a basement foundation with respect to energy efficiency: insulation, water barrier, vapour barrier.

Let's look at the cross section for the basement to see how those factors will be addressed in this Toronto net zero house.

Let's start with the walls.

The main structural component of the wall will be built up of concrete filled ICF blocks. What's an ICF?

ICF or Insulated Concrete Forms, are hollow foam blocks (think styrofoam) which can be fitted together somewhat like building blocks to form walls. Concrete is then poured into the continuous hollow chamber inside the blocks. Once the concrete cures, you've got an insulated, structural wall. The blocks have a foam wall thickness of 2.75 inches (insulation value of ~R27, pretty good already for a basement wall but even more insulation will be added later) which surround a 4 inch core of concrete (almost no insulation value).

Check out the video below to get a better idea of what ICFs are about:



ICFs can be used to build the whole house but they tend to cost more per square foot than building with traditional wood frame so in the case of Adrian's house, he'll only be using them for the basement foundation. To get a fully waterproof, vapour proof, high R-value basement, though, just the ICFs alone will not be enough.

On the outside surface, the surface facing earth, there will be a waterproof membrane applied to it. Sitting against the waterproof membrane will be a dimple membrane which will allow any water which makes its way to the wall to flow down around the footing to the weeping tile where it will drain away. Thus there should be no hydrostatic pressure against the wall and no water penetration through the wall.

On the inside surface of the ICF wall, a 2x4 frame will be built right against it to support more insulation, probably rockwool batte, and drywall. This will provide an additional ~R14 making a total insulation value of ~R41 for the basement walls. Now that level of insulation is something you're not going to find in standard construction.

The floor will be composed of a bottom gravel layer which will hold drainage/venting pipes for water and radon gas. The gravel will be spread out level to the top of the footings.

The next layer of the floor will be a 5.25 inch thick layer of polyurethane foam ( total ~R36) then a water barrier then a 2 inch poured concrete slab. This should be more than adequate to keep water out of the concrete slab and prevent it from seeping up to the basement floor.

Constructed properly, this should result in a very warm, dry and highly energy efficient basement.

The problems with basements

In an urban setting where maximizing space is a major concern, including a basement in the building of a house is almost mandatory. Basements, though, can present a lot of problems if not built properly and looking at some of the on-line literature on basement construction techniques, it seems that until recently, the majority of basements were less than stellar.

Basements are most importantly the structural foundation of a house so they have to be built sturdy enough to solidly hold up everything above it and they have to be able to do it for the life of the house which is certainly expected to be at least several decades long. It's for this reason that most basement foundation walls are made out of cement as cement remains pretty stable even when buried in earth after long periods of time.

The basement should also ideally keep water out and keep heat in and maybe these are a new expectations because it seems that in so many older homes (like mine for example), the basement does neither very well. The inability for basements to do these two jobs properly is not too surprising given that these tasks, especially when required to be done together at the same time, can actually be quite difficult to achieve.

The main problem is that cement is both a water porous material and also a terrible insulator and yet it sits in ground which can be both wet and cold.

Once upon a time, when energy was free, I guess the thinking was that since basements were underground, the earth would act like a good enough insulator and so no additional insulation was necessary. Unfortunately, as it turns out, uninsulated basements can lose a substantial amount of heat, accounting for on average, one third of a home's heating cost.

And also, once upon a time, when we were all made of hardier stuff and a puddle or lake of water leaking into the basement meant free baths, people weren't that bothered with infiltration but nowadays we prefer drier, if possible, and so that means putting up some sort of water barrier.

We've got three components then, a concrete structure, insulation and a water barrier, which we need to put together somehow to hold up the house, keep the heat in and keep the water out. You wouldn't think it would be so difficult to slap these things together and be done with it but it turns out it's not so simple.

Let's take for example what was and for some, still is, a common building method and yet is also what many builders now believe to be a common mistake: We're inside the basement and there's the bare concrete wall and it needs some insulation. Easy enough. Put up a 2 x 4 frame and stuff in some bats of fiberglass. If we just left it at that, the problem is that the insulation is going to get damp and damp insulation is a poor insulator.

The insulation gets damp because of water condensation. It's like in the winter when you see water condense on a cold window except in this case it's not a cold window but a cold concrete wall of the basement. The moisture in the air condenses against the concrete wall which the insulation is pushed right up against so the insulation gets wet and stays wet because water keeps condensing.

In order to prevent this, a vapour barrier can be put up. This can be big sturdy sheets of plastic attached to the 2 x 4 frame which is holding up the insulation. It's quite difficult to put up these big sheets of plastic so that they create a continuously sealed vapour barrier but let's say the installer is successful. The problem now is that the insulation is still going to get wet because the bare concrete wall, as mentioned earlier, is not waterproof, and water from the outside will get in.

There are several ways water can get in past the wall. It may just leak in through cracks and pre-existing seams. It may get sucked up from the ground, called capillary action, similar to the way a sponge absorbs water. It may come from the concrete itself if the concrete hasn't yet cured and dried completely.

So all this moisture gets dumped into the insulation from the concrete side and now that there is a vapour barrier on the other side of the insulation, this moisture is trapped. The insulation is not only degraded but the trapped moisture can also lead to odors, mold and decay.

A water barrier, then, can be applied to the exterior surface of the wall to try to keep any water from penetrating through the wall. This sounds good, but in practice it's really hard to do and if there is any break in this exterior membrane and water gets into the wall, that water will really be trapped for a long time because it is now between two vapour proof membranes.

For a more detailed discussion about these problems and more, you can refer to the excellent Building Science website and this report in particular: Basement Insulation Systems.

You can see how this circuitous process can lead to some major headaches. An alternative strategy, foregoing the interior insulation and putting foam board insulation on the exterior side of the wall, while it may make more sense in theory, can also be tricky to do and has its own set of problems as well.

In recent years, though, builders have come up with some really innovative solutions to address these issues and in the next post we'll take a look at how a lot of these basement problems can be solved using something called insulated concrete forms.

How to get your building permit in 387 easy steps

Adrian asks me if there is somewhere where you can buy a piece of land and just build on it without having to go through the bureaucracy of building permits. I don't know but I'm guessing maybe somewhere in sub-Saharan Africa. Or possibly the moon if it doesn't get privatized anytime soon.

Don't get me wrong. I'm all for building permits, especially in an urban environment. We need some sort of mechanism to protect people from having their houses, or their neighbour's houses, falling down around them because of shoddy workmanship but, still, the permit application process is most definitely a daunting endeavour. It's not for the faint of heart and I'm guessing that's intentional.

It starts with a Pre-Application Applicable Law (PAL) Review. Just look at the title of this thing and you know you're going to be in for a head spin. From the City of Toronto building website:

The PAL Review is a detailed review of a building proposal to determine compliance with various applicable law requirements.

It is an open, flexible program with fewer limits on the number of reviews. Examiners will work with you throughout the process to achieve your goal of obtaining a Notice of Applicable Law Compliance.

I'm not sure what that means but in practice it seems to involve handing in floor plans and building elevations so that someone can tell you if the size and location of your proposed structure is okay. This is where someone will tell you that building a mini-skyscraper in a residential lot isn't going to get approval or that you probably won't get the okay to build a sports arena in your backyard.

There are loads of rules you must follow to get a 100% pass for the PAL Review and I don't know half of them so if you're looking for guidance on that here in this post, you're out of luck. Best to find an experienced designer to help ride out those murky waters if you're building something yourself.

Of course, a lot of builders don't get a 100% pass. The PAL review might tell you, for example, that your building is 6 inches too high. Now you can either go back and change your plans or you can try to apply for a variance from the Committee of Adjustment.

So, I guess the PAL review is basically a foreshadowing of things to come. If you end up with a whole list of stuff that the PAL Review says is going to snag your building permit application, then at least you can do something about it up front.

The PAL Review will also tell you how many thousands of dollars the building permit is going to cost you. It doesn't necessarily tell you how much all the other supporting paperwork on the way to getting the final building permit is going to cost but, hey, I guess they want to break it to you gently.

Adrian's submission went fairly smoothly. The main suggestion after the initial review by the PAL people, was for a survey of the building lot. This is supposedly something new in the process. Previously, surveys didn't have to be done until later but they've been bumped up.

Once you get all the information you can from the PAL Review, you generally start applying for your variances, if you have any, but in Adrian's case, because his lot is on conservation land (ie. there's a big ravine nearby), there's an added step of getting the plans passed by Site Plan Control.

Here's what the official document says about Site Plan Control:

Site Plan Control is an important planning tool for implementing the policies of the Official Plan. A Site Plan Control by-law enables the City to approve the design and technical aspects of a proposed development to ensure it is attractive, functional and compatible with the surrounding area or planned context.

Site Plan Control can also come into the picture if the property has historical value or if there was a toxic waste dump next door or anything else where there is some sort of environmental concern.

Because the build site is on conservation land, Site Plan Control will, at a minimum, ask for an arborist's report so Adrian is now in the process of looking for an arborist. Hopefully, that's all Site Plan Control will ask for but you never really know for sure until they ask for it.

With all this stuff still to do and get approved, it's going to be weeks if not months away from the Committee of Adjustments to apply for variances and then the final building permit application. I'll be sure to let you know how it goes.

Considerations in building a net zero house

In theory, a net zero house is any house which produces as much or more power than it uses. If a household uses 1000 kWh/month (average household electrical usage in Ontario) yet also manages to produce 1000 kWh/month then it is a net zero house. In theory, you don't necessarily need a highly energy efficient house to be a net zero house. In practice, it's a different story. Unless you've got a whole whack of land to mount a large array of solar panels or put up a windmill or dam a stream, it's unlikely producing that much power is a feasible prospect. In an urban environment, it would be especially difficult given the space constraints.

The alternative then, is to decrease household energy usage. The most efficient ways to do this are to:

1. Seal up a house as air tight as possible. This doesn't mean the house gets no air penetration. It means that, ideally, the air flow is completely mechanically controlled so that you get enough air changes per hour to maintain comfort and health while not leaking too much warm air, in the winter, or cool air, in the summer, to the outside. The value passive house builders aim for is .6 air changes per hour or less. In other words, the building must not leak more air than 0.6 times the house volume per hour under a test pressure of 50 pascals when being tested by one of those blower doors.

2. Insulate the house. Taking into account the law of diminishing returns, you don't want to over insulate your house but one standard I'm hearing more about these days is the R-5:10:20:40:60 approach. This suggests that as a minimum there should be an insulation value of R-5 for windows, R-10 for the basement slab, R-20 for the basement walls, R-40 for aboveground walls and R-60 for the roof. If you don't know what all this means, it means a lot of insulation, way more than in the typical house.

3. Use passive solar gain for heating in the cold months as much as possible. This basically means you want your south facing windows to be a big as possible. In the summer, though, you'll need some kind of shading apparatus (like an awning) to keep the sun's heat from streaming in those windows. Flip side of the coin is to minimize north facing windows because they don't really get much solar heat gain in the winter (like none if you're in Toronto) and instead will just allow inside heat to escape because they are, by their nature, poor insulators.

4. Even with an air tight envelope, air (in controlled ventilation) and water will still have to cross the barrier and when this happens, a lot of heat can be carried out. This heat can be recovered using heat recovery devices. For air, a heat recovery ventilation unit, extracts the heat from outflowing air and transfers it to inflowing air. For water, a drain water heat recovery unit, extracts the heat from drain water and transfers it to the water flowing through the hot water line before it gets heated.

5. A heat pump, a device which acts as both an air cooler (air conditioner) and air heater, is an efficient way of meeting any heating demands not achieved by the other systems. Heat pumps are much more efficient at generating heat than furnaces or baseboard heaters and while their output may not be as high, in a well-insulated, air tight house, they should be sufficient to meet the demands.

6. Buy efficient appliances and lights.

There's more, but these are the main points. In designing a net zero house then, great consideration must be given to the envelope of the house, its orientation with respect to the sun, and the selection of highly efficient and complimentary mechanical systems. If money is no concern, a super energy efficient house really isn't that hard to achieve but the goal of this project is to also be cost effective and that presents challenges and some maybe not so obvious choices.

I'll detail some of those choices in future posts.

A modern house

When I was a kid, this was my idea of a house:

I knew that some people built houses that looked like this:but I just didn't get it. Why would you want a flat roof that made your house look like a box when you could have a peaked roof that made you house look like a house?

Well, many years later, while some tastes have stayed the same (milk chocolate over dark, French fries over mash) my preference in houses has slowly moved from traditional to modern.

I still appreciate a well designed, well built traditional home but it's the look and the feel found in modern styles that really pique my interest these days. As defined by Wikipedia: "Modern architecture is characterized by simplification of form and creation of ornament from the structure and theme of the building." Or, in other words, you won't likely see gargoyles ornamenting the roof of a modern house unless the gargoyles are helping to hold up the roof. Every part that goes into the build of a modern house has a purpose - in theory anyway. In practice, well, there's no point in being obsessive-compulsive about it.

Here are some renders of the house to be (click on image to enlarge):





Here are the floor plans:

Basement

1st Floor

2nd Floor

It's a two story building with a half basement (other half being the garage) and a walkout to the roof. The total livable space is about 1700 square feet.

The front of the house, which is south-facing, has large window areas to take advantage of solar gain in the winter. Some sort of shading device (possibly incorporating photovoltaic solar panels) will be added to block out the sun in the summer.

Some variances will be required from the city but those will be addressed in a later post.

In laying out the interior, the idea is to create an open public area on the first floor with a more traditional three bedroom layout on the 2nd floor. The neighbourhood the house is situated in is more geared towards families so the third bedroom, as opposed to, say, an interior balcony overlooking the first floor or a spa sized bathroom, is thought to be a more suitable choice.