energy consumption

The Path to Decarbonization and Net Zero Energy

October 13, 2016 by clove Leave a Comment

We’re targeting net-zero energy consumption and zero carbon emissions in the operation of our post-project home. Say what?

Net zero energy means that, on an annual basis, we generate as much energy as we use. So unless we have an oil well on our property, we are drastically reducing both our fossil fuel consumption and our utility grid dependence. Zero carbon emissions simply means that we don’t burn any fossil fuels to operate our home.

A home could use one or more different sources of site-generated renewable energy – solar photovoltaics or solar thermal, for example. I’m keeping things simple for the moment by assuming that we will only use solar photovoltaics to generate electricity. Unless we include battery storage, we will still be drawing electricity from the grid when the sun isn’t shining or when our demand is higher than our panels can provide. But in a place like BC that has a net-metering program, we will also be feeding back into the grid when we’re generating more than we need.

So can anyone just plunk a bunch of solar panels on the roof and viola: net zero energy? Not so fast. With the amount of energy most houses use today, you’d need a much bigger roof than you have. Allow me to demonstrate with our existing house.

In an earlier post, I estimated our current annual energy consumption to be about 13,270 kWh per year, or ~120 kWh/m2 of conditioned floor area, based on our first 6 months of utility bills. This is actually an ok number given that we have three chimneys, single pane windows, and all sorts of leaks and drafts. It’s about 45% lower than the average Canadian home and on par with the Germans. We turn things off when we aren’t using them, but we also shiver through the winter with an inadequate heating system.

We now have a full year of electricity consumption data to update my earlier guestimate. Our actual one-year consumption was 13,700 kWh, or 123 kWh/m2/year. The daily consumption curve looks like this:

Full year of energy consumption for our existing house

The ‘curved’ part is the energy we used for heating. If you drew a straight line across the flatter portion of the graph, the area below the line would roughly represent our non-heating energy use, which stays relatively constant throughout the year.

So that’s the energy demand side. Let’s now turn to the solar PV question.

I called up Power to the People, who will do a free, high level evaluation of the solar potential of your house, based on a google earth analysis, some rules of thumb, and an assumption that your roof is not shaded. Here’s what their evaluation spat out for our existing house:

Power to the People Solar PV Analysis

If we covered our south, east, and west roofs with panels, we could generate 7150 kWh annually. This is a little over half of our current consumption. We would have to reduce our consumption by nearly half to achieve our next zero energy vision using only solar PV.

Is this even possible? The Passive House approach promises a 90% reduction in heating demand by focusing primarily on the design of the building envelope. According to my rough estimate, about 50% of our current consumption is for heating. So it would be doable if we both dramatically reduced our heating demand by improving the envelope and found some additional ways to save. I predict, for instance, that my long hot shower habit will be curbed when our house feels warm and comfortable in the winter. We’ve also heard that people who live in passive houses do not use dryers because the heat recovery ventilator helps clothes dry so quickly.

So we think it’s challenging but doable, and our example illustrates two things:

The first step must be to reduce demand through passive strategies, like extra insulation, increased air tightness, and better windows.
The way you live in your house matters too! Turning off lights and electronics, limiting long hot showers and dryer use etc. The lower you can get your energy demand, the more likely you can meet your annual average with site-generated energy.

One of the most exciting prospects about following the passive house approach is that we can reach our goal while feeling WAY more comfortable and having WAY better air quality. Win win!

On Courage and Cool Projects

April 8, 2016 by clove Leave a Comment

We are (still!) in the midst of neighbourhood consultation, and I will provide an update on that process very soon. Suffice to say that I occasionally wake in the middle of the night feeling anxious and in need of a fresh burst of inspiration. So for this post, I am sharing some big ideas from beyond our small project.

Last month I attended the Passive House Northwest Conference (PHNW) in Portland Oregon to present the research RDH is doing at the North Park Passive House here in Victoria. I left the conference full of admiration for the people making incredible projects happen on our continent. And it really is about the people. These projects do not just materialize on their own accord. The people who are making them happen display incredible depths of courage and tenacity. Here I introduce you to two of these people and their projects.

Arnold Development Group’s Second and Delaware project; rendering from Arnold’s PHNW presentation

Jonathan Arnold, President and CEO of Arnold Development Group, for his triple bottom line development model (one look at his Advisory Board will tell you this is a company committed to doing things differently) and his latest project at Second and Delaware in Kansas City. This project I love because it addresses everything that matters today in terms of development: energy, housing, food and transportation. It is a higher density rental project in the heart of the city that uses a traditional courtyard design. It is walkable and transit oriented. It is designed to meet the Passive House standard. It includes a diversity of housing types, including 20% ‘workforce’ housing. It includes space for urban farming. It is a place where people will want to live, can afford to live, and can do so with a light environmental footprint.

You can download his presentation from the conference here.

Second and Delaware features; from Arnold’s PHNW presentation

Lois B. Arena, Senior Engineer and Passive House Consultant at Steven Winter Associates , for driving the design of the world’s largest Passive House building – the Cornell Tech NYC Campus Residential Building, now under construction.

Cornell Tech NYC Residential Building, rendering from Arena’s PHNW presentation

Imagine that the fasteners that Lois needs to attach curtain wall with no thermal bridging did not exist before her project. She is drawing completely new details and training contractors. She is having to change existing building code to design the mechanical ventilation system. She is the one telling the contractors that they are simply going to have to do things differently – and she’s undoubtedly repeating this message over and over again. She joked about going grey within a couple of months of the start of construction, but what an accomplishment it will be after it’s complete.

Lois’ presentation (which will particularly appeal to the techies in the crowd) can be downloaded here.

When I see the sprawl in the outer edges of our city and the construction practices that focus on short term profit, I lose heart that things will change and change fast enough to have a real impact on climate change. Then I see projects like these. Big projects in big cities. People who are showing that it can be done and that designing for the environment goes hand in hand with fiscal common sense.

Returning to the really big picture, I want to close with an invitation to view Zack Semke’s fantastic keynote presentation at PHNW, which ended with a standing ovation. Zack opened with the worst case scenario: If we burn all remaining fossil fuels, Antarctica will melt and sea levels will rise by 200 ft. He asked: Are we all f****d no matter what we do?

I highly encourage you to flip through his slides – at turns shocking, hilarious, and inspiring as the key messages will shine through without having heard the talk. Below is an excerpt – a graph of the relative prices of gas, coal, oil, LNG, and solar. The plummeting grey line is solar, and may represent what is called a “Black Swan” event – an event that changes everything and seems to have come out of nowhere. The internet is a black swan event. The plummeting price of solar PV? Could be a black swan event.

Price of Solar PV vs gas, coal, oil, LNG.

Zack’s call to action is to resist climate denialism (there is no problem and/or we’re not part of the problem), overcome climate defeatism (we’re all f*****d anyway), and continue to take small local steps toward potentially huge collective change. Three cheers for courage and cool projects.

How Much of an Energy Hog is Our Existing House?

March 18, 2016 by clove 4 Comments

Our goal is to create housing for 2.5 families that uses less energy than the existing single family house. So how much of an energy hog is our existing house?

Here’s what our daily energy consumption looks like for the first 6 months we’ve lived here, starting in July 2015:

So…is this a lot?

Let’s do some very rough comparisons. I’ve doubled our first 6-month consumption to estimate annual consumption; converted to a per square meter metric and then compared against some other references:

Canadian average consumption for a household our size, kWh/square meter/year
Our existing house consumption, estimated, kWh/square meter/year
A typical German house, kWh/square meter/year
The first local certified Passive House (Bernhardt Passive House), kWh/square meter/year*

*We’re just talking ballparks here. It’s pretty difficult to find comparative numbers that all use the same assumptions – my intent is to show a reasonable range in potential consumption.

Hey! We’re actually doing really well by our abysmal Canadian standards, and pretty average by German standards. Of course, we would expect our consumption to be lower than the Canadian average because we have the mildest winter in Canada, although it’s unlikely to result in this much of a difference on its own.

But wait – this is only part of the story.

The other part of the story is that, boy, were we cold over the winter!

Our house came with an oil furnace and an empty tank. We didn’t want to buy a full tank of oil to heat the house for a winter when we’re getting rid of this system with our renovation, nor did we particularly want to use the existing duct work. The previous owner was a smoker and lord knows what might come puffing out of those ducts. Better to let sleeping dogs lie.

Matt cobbled together storm windows for some of our original single pane wood windows, and we put plastic film on the inside of others. And we shivered through the (albeit mild) Victoria winter, with two wall-mounted electric baseboard heaters and 2 plug-in electric heaters. We moved the heaters around depending on what room we were in and closed doors of rooms we weren’t in.

In conclusion, then, our existing house isn’t an energy hog based on the way we’re currently running it, but it surely would be one if we heated to a modern-day standard of comfort.

This comparison shows very clearly the range of what is possible. I think we can hit our target compared to what a typical house in our climate consumes. And I for one am looking forward to experiencing the comfort promised by a well insulated, airtight, and properly ventilated house!

Passive House, Net Zero, or just a Pretty Good House?

August 16, 2015 by clove 2 Comments

Here’s the lowdown on our current favourite approaches to achieve our project’s energy performance goals. We’re more interested in the principles than checking boxes or getting a plaque, and want to pick and choose what will work best for us. (And yes, there are other important goals like low water consumption, healthy and local materials, and creating something beautiful, but today we’re talking energy.)

Passive House
Net Zero House
Pretty Good House

Passive House:

The Passive House standard has 3 key performance requirements:

Annual heating demand <= 15 kWh/M2/year. This is a 70-90% reduction over what most houses use for heating.
Total primary energy demand <= 120 kWh/M2/year (this is a measure of total energy consumption, including the energy required to generate and transport the energy from the source, using a single source energy factor for all of North America)
Air tightness, as Air Changes per Hour (ACH) <= 0.6 ACH50, as measured by a blower door test. This is about 4 times more airtight than a typical new house.

Here’s a snappy video that explains the fundamentals of the Passive House approach:

The basic concept of the Passive House standard is to focus first on the structure itself: highly insulated foundation, exterior walls, roof; airtight enclosure, and high performing windows – and then supplement with mechanical heating and/or cooling systems. So we reduce demand as much as possible first before looking at efficient ways to provide the remaining energy we need. Mechanical ventilation is also required to maintain air quality.

The requirements are performance based (focused on the end result rather than prescribing certain systems or building elements), but they do lead us to certain choices that we must make in order to meet the requirements, such as triple pane windows, very high performing heat recovery ventilators (HRVs), and thermal bridge-free construction. Equipment and windows must also be tested specifically to Passive House specifications, which can limit the available choices of certain products like HRVs.

Passive House does not require site-generated renewable energy, although it does provide a credit toward primary energy demand for on-site solar PV.

Passive House performance is modeled using PHPP, which is a giant spreadsheet that does a lot of backend calculating based on heat loss, heat gains, and local monthly average climate data.

For smaller buildings like ours, we will have difficulty meeting the standard without good unobstructed southern orientation (although there are a couple of new certification options that offer some hope – post to come). The south side yard is especially challenging because butting up against our desire to maximize south-facing windows are perfectly reasonable zoning requirements intended to protect the privacy of our neighbhours. Depending on the distance of the house to the property line, we are limited in the amount of glazing and the rooms in which we can have glazing facing the side yard.

What we do have going for us is a simple shape: both houses will basically be rectangles, which makes the detailing for no thermal bridging and a continuous air barrier much simpler (the less corners the better).

Regardless of whether we meet or seek official Passive House certification, I think the passive approach is common sense for any building anywhere, and this will form the foundation of our design approach.

Net Zero

Net zero energy means that, on an annual average basis, our project produces as much energy as we consume. Net zero carbon emissions means that we either purchase carbon offsets, or we avoid the use of fossil fuel based energy.

Can we produce on-site as much energy as we consume in a year? This will depend on three key things: the design of our enclosure to minimize energy loads, our behaviour as energy consumers, and the amount of solar PV capacity we can fit on the roof. In our case, BC Hydro allows net metering, so we can feed excess generated energy back into the grid, and draw it from the grid when we are in deficit.

Passive House does not require the use of on-site renewable energy, but it makes net zero energy consumption viable because it significantly reduces demand.

We’ll have to do some modeling to look at the solar potential of our roof in our specific location, as well as take a stab at estimating our energy demand to get a better sense of where we’re at.

I think this is a goal worth shooting for. We will design for an all-electric project with solar PV, since BC produces much of its electricity using “carbon-neutral” hydro electricity.

The Pretty Good House

The Pretty Good House is not so much a standard as a practical discussion happening on Green Building Advisor. It’s about making realistic choices based on the best bang for your buck in your climate, and still, by the way, ending up with something way better than code minimum. So not going quite as far as Passive House, but, say, 80% of the way there.

We’ve also seen a big variation in the actual energy consumption of certified Passive Houses, which reminds us of the critical importance of occupant behaviour. How does the impact of behaviour compare with the impact of a well designed home?

I like the Pretty Good House approach – and I would argue that it can lead us to a Really Good House – but it does require a sound understanding of the fundamentals. This is why programs like Passive House are great, because they work as learning tools.

So in summary, we will be applying passive house principles, striving for net zero energy consumption, and hopefully ending up with a couple of Really Good Houses. I am fortunate to work with a bunch of building science geniuses at RDH, who will help us get the details right.

Our project gives us a unique opportunity to compare an existing house retrofit to a new build on the same site, which is very exciting. There is also a new, slightly relaxed Passive House standard that was just released, designed for small houses on constrained lots like ours, so that might prove a viable option for us.

We will document our before and after energy consumption and share the results here. Stay tuned!

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