West Bay Passive House

One of the goals in building our Passive House was to educate and show people what can be done without a large incremental cost.   I believe that our children are way more aware and open minded to sustainability and preserving our planet than our generation.  My son and I presented to his class on our new house and I was blown away with the questions and the enthusiasm from the kids.  Here is a copy of our powerpoint presentation.

Passive House_West Bay Presentation_v1

Written by Stuart Hood and Thomas Bamber from the Integral Group

The mechanical system at the Radcliffe Passive House was designed to achieve year-round comfort from minimal energy consumption. We wanted a highly efficient HVAC solution that achieves simplicity through a limited number of components.

Prior to selecting systems we needed loads for each space. From conception the house had been designed according to Passive House principles that minimize the thermal energy demand. PHPP modelling had calculated a peak heating load of 2.8kW and peak cooling of 2.5kW for the whole house. Our mechanical consultants Integral Group undertook an alternate analysis using an hourly thermal modelling software, EDSL Tas.

Given the large amount of glass on the south face of the home our one concern was overheating. We wanted to test whether supplementary cooling would benefit the heavily glazed Living Area and Master Bedroom at the top of the house. We modelled the house under a Vancouver and an Abbotsford weather file with higher temperatures, to be conservative and allow for an increase in temperatures due to climate change.

The thermal model showed that despite the shading from the overhangs, solar gains were an issue. Reducing the solar heat gain coefficient (SHGC) of the glazing from the design value of 0.69 to 0.42 cut peak cooling in the Master Bedroom from 2.5kW to 1.7kW for the scenario of an Abbotsford summer with thermostat set to 25degrees (in line with PHPP). Even with improved glazing, the total cooling load for the house was calculated at 4.4kW; roughly double the PHPP model.

The simulations also demonstrated that the operable windows and sliding doors situated throughout the house can create generous airflows in summer. The free cooling generated from natural ventilation can be used either as a mixed mode system with mechanical ventilation or even as a stand-alone solution for preventing overheating. We tested the performance of natural ventilation without mechanical cooling and found that many of the spaces passed the overheating criterion CIBSE TM52 – an established benchmark for summertime comfort in naturally ventilated buildings.

On the basis of the thermal analysis, we improved the SHGC of the whole house and provided top-up cooling to the Master Bed only using a Jaga fan-coil. All spaces would have cooling via the mechanical ventilation system and the option to boost airflow by opening windows.

For the heat recovery ventilation system we specified a Zehnder Energy Recovery Ventilator (ERV) with an 89% thermal efficiency plus latent recovery. One unit supplies and exhausts from the whole house, including washrooms. Instead of ductwork we used a prefabricated Comfotube duct system, which integrates cleanly with the architectural design. Spaces requiring greater airflow are provided with additional 3″ plastic Comfotubes. In keeping with the mantra of heat recovery, we are installing drain water heat recovery using a PowerPipe which recovers heat otherwise lost from the bath and shower drain water and transfer it into the incoming cold water make up to the hot water tank and shower mixing valve cold water pipe.

It was calculated that we could deliver both our peak heating and cooling using a 2-ton Daikin Altherma air to water heat pump. The Altherma also provides domestic water heating, with a top-up immersion heater. The heat pump can switch between heating and cooling, so in summer the hot water tank is kept full, while the house is cooled. To deliver heat and cool air around the house, we took advantage of the ventilation system by installing 2 coils in the Zehnder ERV supply air discharge to allow for two separate zones in the house.

What makes this so simple and efficient is the absence of pipework and terminal units. Heat is pumped to the ERV Comfocoil and to one additional Jaga unit coil in the Master Bedroom. To make this strategy work, the ventilation air (and hence heat supply) had to be carefully balanced around the house. When peak summer and winter conditions occur, the unit can step into ‘boost mode’, increasing the heating or cooling output through greater air supply. There is also local heating top-up provided by towel radiators, Nu-heat electric floor heat in the bathrooms and a wood burning sealed combustion high efficiency fireplace in the Living Area from Stuv.

We used Tekmar Controls to bring everything (even the towel rails) onto a centralized panel and allow remote control and monitoring from a smart phone or tablet.

With this simple mechanical design and taking advantage of the excellent building envelope, triple glazed glass and over hangs of the Passive House we are able to eliminate the cost and complexity of traditional heating and cooling systems like ducted force air, VRF or in-floor radiant.

This design of the mechanical system in the Westbay Passive House will bring excellent comfort, energy efficiency, lower cost and healthy indoor air for the Dean family.

One of the key principles in Passive House construction is to have well insulated walls, roof and floors that are also air tight.   We looked at a couple of different options including building on-site or going with prefabricated panels.  We decided to go prefabbecause it will shorten the construction schedule by a couple of months and the quality of construction will be better with them built inside a factory.   There are two different approaches to pre-fab.  BC Passive House in Pemberton makes a 2×6 framed wood wall with cellulose insulation  and CutMyTimber in Portland makes Cross-laminated timber-CLT wall, floor and roof assemblies with a Roxul mineral wool insulated that goes on the outside. Cross–laminated timber (CLT) is a wood panel typically consisting of three or five layers of dimension lumber oriented at right angles to one another and then glued to form structural panels with exceptional strength, dimensional stability, and rigidity.  In the picture below the 4 1/8″ dimension is the CLT wall panel and the 6″ dimension is the Roxul insulation, the 8″ dimension is the concrete footing and the 3 1/2″ dimension is an interior wall cavity for running utilities. We are using the CLT panels with Roxul because of the strength, insulating value and the manufacturer could meet our construction schedule.  CutMyTimber is just finishing up the shop drawings and the panels should be finished by Christmas for installation with a crane in January.

 

We had a meeting with the Mayor and City Councillors of West Vancouver to get approval on a couple of variances for the house that we were requesting.  The first was a variance on the height because the solar panels put us over on the maximum allowable (though were still below the height of the peak of the existing house) and the second was to ask for an 179 ft2 of FSR (allowable floor space) to make up for the lost area because of the additional 5 inches of insulation in the walls.   I was a bit nervous going into the meeting but was hopeful with the support from the city staff, I had also met with two of the Councillors in advance to get their support, had 12 of our neighbours sign letters of support and West Vancouver has recently adopted a Community Energy and Emmissions plan to encourage energy efficient buildings.  Special thanks to Councillors Nora Gambioli for her support and Bill Soprovich who came and toured the property and ask lots of good questions about Passive House.  Here is a link to a video of the meeting.  https://westvancouver.ca/government/mayor-council/council-videos on May 1st.  Some interesting parts are:

• 6:39:17 – The city staff presenting the project to council
• 6:43:43- Me giving my pitch on why we are building a Passive House and asking for Council’s support
• 6:52-  Questions and comments from the Councillors and Mayor

I am pleased to report that the vote from council was unanimous to support the variances.  Thanks to the Councillors for their support and encouraging words and our neighbours who have been very supportive as well.

After speaking with many people who have renovated and built new homes the number one piece of advice I have gotten is to pick the right team of architects, builders, engineers and tradespeople to work with.  People that you can trust, like, have a lot experience, strong references and a similar vision for what we want to build.

Being an analytical person I started by preparing a matrix with my criteria for evaluating each of a short-list of the different consultants to work with.   For our architect my criteria was:

• Do we like the design of the previous homes they’ve designed
• Do they have Passive House or Green Building Experience
• Strength of the references
• Experience of the firm and depth of the team
• Is there a personality fit…do we like them
• Design Fees
• Expected cost to build the home
• Are they a recognized firm

After interviewing 3 excellent firms and meeting with several of their previous clients we selected Battersby Howat http://www.battersbyhowat.com/ and have been working with David Battersby, Heather Howat and Bettina Balcaen over the past year.   They are amazing at what they do, fun to work with and we love the design they have come up with.  While Battersby had never designed a Passive House they had similar values to us around sustainable design, had take the Passive House course and we could tell were really enthusiastic to work with us our project,

We went through a similar approach with builders and selected Naikoon    http://www.naikooncontracting.com/ after discovering that we knew 5 different people who have used Joe Geluch and his team and all gave outstanding references.   We have been working with Naikoon for the past few months as we prepare the site and work towards getting our building permit.  I have liked their strong project management skills and open communication.

We selected Marcel Studer from http://www.econgroup.ca/ as our Passive House Consultant who is very experienced on Passive House having designed, built and consulted on many Passive House projects and teaches the Passive House course in Vancouver.

Thanks to Stuart Hood from the Integral Group http://www.integralgroup.com/ who has been advising me on the design of the mechanical and HVAC system.

I also decided to hire Haron Douglas who is a Quantity Surveyor to prepare a detailed estimate of what the estimated total project cost will be and was very pleased with his work.

We have been speaking with Stefan Schneider from http://www.cutmytimber.com/ who specializes in prefab wall and floor assemblies.

Unfortuantely have had to make one change with one of the consultants hired part way through the project but I felt that if we were not satisfied with the work at this point in the project it was best to deal with this early and switch now before it further impacts the schedule and costs later.  A point to note is that this was the one consultant that I didn’t meet prior to hiring them which in hindsight was a mistake.

We are extremely happy with the team we have assembled and are all experts in their field, have been easy to work with and are like minded in the Vision we have for our Passive House.