top of page

The Simplest Path To An Energy Efficient Multiplex (And How To Avoid A Costly PMT)

Anyone building a multiplex may need to install an expensive pad-mounted electrical transformer (PMT) that eats up valuable floor area, but there are several relatively simple things that you can do to lessen the likelihood of needing one and make a more comfortable building at the same time.

The Pad-Mounted Transformer

simulated photo of a PMT in front of a modern multiplex, summer, grass, sunshine

In this article, I explain three things that you should explore as relatively simple - and comparatively inexpensive - things to incorporate into the design of a new multiplex. Something that catches some owners and designers by surprise is the potential to require the installation of a pad-mounted electrical transformer (PMT). The City of Vancouver's R1-1 Housing Options Guide explains how you need to make allowance for a PMT as part of your development permit application.

... a development condition to reserve space on site for a transformer will be placed at the time of application for projects with more than three units. ... It is the applicant’s responsibility to contact BC Hydro before submitting a development application to request an evaluation of the proposed service load and size to confirm if a transformer is required.

Unshackled From The Box

simulated photo of a PMT at dawn in front of a house

The installation of a PMT - which will likely cost $50,000 or more in British Columbia - takes up valuable space on your site - at least roughly 80 square feet for the main floor of a rear building and just as much for a second floor of a rear building. For a 33' wide lot, this results in an otherwise unnecessary structural jog in the rear building, takes up one parking stall, and is unappealing aesthetically. For properties with a PMT, extra electrical equipment is required in the building - again taking up more valuable space.

However, the addition of a PMT isn't a given; the design of your multiplex can reduce the electrical requirements ("proposed service load") possibly to avoid adding a transformer. If you don't need to have a PMT installed, you've saved tens of thousands of dollars. You can also rent or sell an additional parking stall or design a simpler rear building, which lowers the overall cost of construction.

Lighten The Load

The City of Vancouver Building By-Law (VBBL) and the British Columbia Building Code (BCBC) both impose limits on greenhouse gas intensity. In short, this means that you will be limited in what natural gas equipment you can use; Vancouver and the province are both pushing for electrification of homes. This electrification of homes means the electrical load goes up, right? As well, the simultaneous densification of neighbourhoods results in greater electrical requirements for the area, which could exceed local infrastructure. Everyone wanted to buy a Tesla Model 3, so the price went up and availability went down.

simulated photo of a PMT in front of a modern multiplex, summer, grass, sunshine

How can you electrify while everyone else is doing the same, and also avoid the need for this expensive, large equipment? There are a raft of options and strategies - enough to make a novice's head spin and even give many designers and architects a headache. Therefore, I will keep it simple and showcase the three simplest measures.

You may wonder: do these three measures cost anything? Yes, they have a cost, BUT the target is a bigger savings, more useable area, AND a more comfortable home for family, tenants, or buyers (which can translate to greater financial return). You get back MORE than what you put in. You don't need to build a Net Zero, Passive House certified, or any other "Zero Emissions Building" to get enough benefit to help your project.

Where's The Money Going?

Consider a piece of equipment - for example your furnace - that needs 100 Blargs of energy to run. It doesn't matter if we're discussing a single house or a multiplex; the concept applies similarly to any residential building. Currently, those 100 Blargs of energy are provided in the form of burning natural gas. The furnace needs 100 Blargs because your building is thermally inefficient and needs lights all over so that it's not dark. Or maybe you have massive windows everywhere, and your furnace needs 120 Blargs and your AC system needs 150 Blargs.

BTW, yes I just made that word up.

simulated photo of a PMT at dawn in front of a house

So being forced by the baddies in city hall to switch to electric means you need 100 or 150 more Blargs of electricity than before electrification... which now pushes you into needing a PMT. Is it the electricity's fault? NO. It's the building's inefficiency, so let's improve on that. Let's bring the total need down to maybe only 50 Blargs.

#1 Windows

You want plenty of natural light of course, but you actually want it for two reasons. The first is obvious - a brighter indoor environment. You get more pleasant, more functional spaces. You also don't need as many luminaires (the correct term for light fixtures). Big windows will give you lots of free light. While running a hundred luminaires with LED bulbs is less energy-intensive than a hundred incandescent bulbs, it's still measurable.

simulated photo of large windows in home looking out to Vancouver coastal forest and daylight

The second reason is free heating. For between half and three-quarters of the year (depending on your locale and exposure), that great amount of sunshine is valuable; it offsets your need for Blargs to heat the space. Unfortunately, most large windows create glare and take in too much heat. When the sun isn't shining through them (winter, nighttime), they lose too much heat. Control of this heat is key to climate resilient construction.

The solution here is very high-quality windows. You need more than just "triple-glazed windows"; you really should aim for Passive House certified triple-glazed windows even if you're not doing a Passive House building. There are six local (BC) manufacturers of Passive House certified window frames - both fibreglass and wood. At the moment though, the sealed glass unit that fits in the frame before it is brought to your project, is still manufactured overseas - typically in Europe. The higher product cost and installation cost of these very heavy Passive House windows is worthwhile though, for several reasons:

  1. The edging of the glass unit performs better at preventing heat moving through it.

  2. The seal of the glass unit and of the frame is much better and will last far longer. This is important because air leakage through the frame of your window is another way you can lose heat in the winter or lose air-conditioned air during the summer.

  3. The glass itself is treated to reduce the amount of the infrared portion of sunlight; this is the portion that is most responsible for a room heating up. You want as much visible daylight as possible but less solar heating.

  4. More daylight means less artificial lighting and hence lower electrical requirements.

#2 Self-Adhesive Exterior Air Barrier

As mentioned above, warm indoor air can escape during the winter, and AC-cooled indoor air can escape during the summer. This isn't news; everyone has heard of the importance of sealing gaps around doors and windows since the oil crisis of the 70's. In actual construction, the white-coloured building 'paper' (sometimes called housewrap or Tyvek) does not effectively prevent air leakage through the exterior walls because of all the penetrations (pipes, exhaust vents, wires). As high-performance home construction has matured, those on the leading edge have come to understand also that the clear plastic sheet (polyethylene in Canada and the northern US) that is stapled to the interior side of studs doesn't effectively prevent air leakage either.

simulated photo of a house wrapped in plastic sheeting

Instead, a self-adhesive synthetic fabric sheet - or membrane that is applied as a liquid - does a far better job at keeping the walls airtight. This membrane acts as the "air control layer" or "air barrier". There are other benefits to a better air barrier than the compromised polyethylene or housewrap, and you can read about them in my article, HEALTHY HOME DESIGN: Better Indoor Air Quality Using Better Air Barriers.

Two very important things need to be kept in mind with a better air barrier though.

  1. You should invest in a heat recovery ventilator (HRV) since all the cracks and holes in your walls and roof were how fresh air was supplied to your indoor space when the windows are closed and the furnace isn't running (e.g. nighttime spring and autumn). The HRV (or ERV) supplies fresh air constantly to your whole building. Read more in my article HEALTHY HOMES: Breathing Better and Saving Money With A Heat Recovery Ventilator (HRV).

  2. A gas fireplace or - even worse - a gas stove becomes a greater health hazard since the wind isn't blowing through your home and flushing out the toxic particulates from leaking gas lines or incompletely burned gas.

#3 Extra Exterior Continuous Insulation

With new, more stringent energy efficiency requirements, some builders react by switching from 2x6 exterior wall studs to 2x8 studs since it increases the amount of insulation. However, the studs are more expensive, and the additional insulation isn't as effective since the studs are still conducting heat through the wall. I won't get any more technical in this article, but there's plenty you can find on what is called "thermal bridging".

illustration of a personified house standing in the snow with a heavy sweater

Providing a thermal insulation layer between the exterior plywood sheathing and the siding material eliminates most of the thermal bridging. This is more often a semi-rigid (squishy) mineral fibre insulation type - usually Rockwool / Roxul - but occasionally a Styrofoam board (pink or blue); it is separate from the fluffy insulation batts that fit between the studs. The challenge that most teams face is how to secure the siding (wood, stucco, Hardie, brick) when the insulation is continuous. A local design-builder developed an excellent and practical fastening method, so this exterior insulation can be implemented easily.

BONUS: Heat Pumps

As I finish writing this article, I realize that it would be unfair to leave out this one: heat pumps. However, they're a pretty meaty topic, and I have a few articles that do a great job of explaining them, such as this article here: DESIGN FOR CLIMATE CHANGE: What Is The Cheapest Way To Heat And Cool Your Home?.

simulated photo of a heat pump beside landscaping  beside a house at dawn

My focus is ultra high-performance houses and multiplexes - what I call the UltraHome and the Invisible Multiplex. By leveraging the lessons learned by private and publicly funded developer teams and builders of Passive House construction, I can design better buildings for lower cost. More people across the Lower Mainland are therefore able to afford to build - and able to build better homes.

BC Hydro

While none of these strategies is a guarantee that you won't need a PMT or even a low-profile transformer (LPT) - or even that you'll be able to proceed with constructing a multiplex - they will help you substantially lower the likelihood and result in a more comfortable set of homes.

Process For Winners

Even with the City of Vancouver multiplex design guides and BC Hydro Landscaping guide for transformers, there are many things to organize when starting the planning phase of a construction project. You can download my free Project Planning Package by clicking on the button below. It gets you to ask yourself some important questions, sort out some costs, look up important regulations, and map out the process from research to moving in.

illustration of a generic process flowchart

You could adopt a solid strategy that incorporates cost-saving and performance-enhancing techniques. The result would be a more comfortable home for extended family, a rental property with higher revenue, or a stratified property that sells for more.

On the other hand, you could follow the status quo, be in the same boat as everyone else, and struggle with high construction costs just to meet the building code... and face a higher chance of that lovely PMT in your back yard.

thumbnail of a project planning package

If you're ready to discuss your project with an architect, you can book a free, 30-minute Diagnostic Session by clicking the link below.

In this call, we'll discuss your options for moving forward with the project. You'll come out with a clear plan of action.



The information included in this article is to an extent generic and intended for educational and informational purposes only; it does not constitute legal or professional advice. Thorough efforts are made to ensure the accuracy of the article, but having read this article, you understand and agree that Daniel Clarke Architect disclaims any legal liability for actions that may arise from reliance on the information provided in this article. I am an architect in BC, but readers are recommended to consult with their own architect on their specific situations before making any decisions or exercising judgement base on information in the article.



Commenting has been turned off.
bottom of page