Comparing Notes: Lessons Learned on Passive Building
Lessons from a developer, some architects, and energy modelers on the front lines of PHIUS+
"As an architect, to suddenly learn that everything I knew was wrong. You can't unlearn this stuff, and once you're aware of it, everything around you seems—negligent."
—Sam Rodell, Architect
Rodell does not blame negligence on people who don't know what they don't know but notes that it seems negligent that within the design and construction sector of this vast economy, that passive building techniques are so foreign to so many.
With that in mind, here are some lessons learned from the front lines of PHIUS+ projects:
1. To do passive building, you need a great team
"The reality is that if you are doing a standard project, everyone has done 20 or 30 projects. Collectively, you've done hundreds of projects. On a Passive Building project, the experience is not nearly as deep. Everyone may have done one or two projects. The collective wisdom is much more shallow. Check your ego at the door because you’re probably going to be wrong about most things that you would normally do on a project. Hopefully at the end, you’ll get something that really works."
—Sloan Ritchie, Developer
"These projects demonstrate the importance of integrated design: architecture, structure, and mechanical systems can achieve much more together than separately. Rodell brings in a general contractor—preferably a certified PHIUS builder—as early in the process as possible. As the design progresses, they bring in subcontractors and get to a granular level of planning and trade-offs through the 3D energy models.
Becoming a Certified Passive House Consultant takes about a couple of weeks of your time. Builder training is even less. Both are well worth it."
—Sam Rodell, Architect
"We were lucky to have a site-superintendent that was very keen on the success of PH targets, and willing to put in extra effort - not always the case in Design-Bid-Build projects."
—Valley Waste Management design team
"Use an aggressive contract. Passive building is gaining steam, but there are still a lot of building and design professionals with little or no experience in it. Even highly experienced professionals can miss critical details in something they’ve never done.
One way RMI kept the team focused was to put performance in the contract. One example is that they set the passive house airtightness target as a requirement for multiple trades, and it was included in their contracts."
—RMI Design team
2. Modeling is powerful
"Iterative energy modelling is crucial in the early design stages."
—Valley Waste Management design team
"Rodell Architecture is a Revit shop—BIM software—and Sam says that they "...are heavily into it. We build the site before we do any design work, and then we do all of the design work in a three-dimensional context, in Revit. We have been doing that for years. We now use our Revit models and export them into WUFI Passive (PHIUS+ software), so we have three-dimensional energy models."
Those models have become a critical and informative part of the design process, right at the schematic phase. So they have the information they need—while they are working in real time—to see how things they do affect the design as it progresses."
—Sam Rodell, Architect
3. Keep it simple
"Use passive measures before active, THEN use simple systems. Even though we had a simple mechanical system. It took significant effort to get the thermal and ventilation building controls to work properly.
Another KISS tip: make it hard for the contractor to mess-up the envelope. We placed the air-vapour barrier on the outside of the stud cavity, reducing the chance of electrical and plumbing penetrations, and allowing for things such as picture hanging to not compromise air tightness."
—Valley Waste Management design team
"'Oversize' the insulation instead of HVAC. Insulation is less expensive than mechanical equipment, and it has fewer moving parts, so it never really needs maintenance. Overinvesting in insulation means that the mechanical systems will have less work to do, so they can be smaller. Or nonexistent. The RMI heating system runs comfortably at ⅓ capacity thanks to superinsulation.
—RMI Design team
"Four inches of outboard Rockwool was a challenge for the siding contractor. He walked off the site, so we had to find another siding contractor."
—Sloan Ritchie, Developer
4. Nonstandard HVAC can complicate the process
"The baseline in Seattle is trickle vents and K&B exhaust fans. Anything you do on a Passive Building project will be more expensive."
Trickle vents require no ductwork, they are cheap, and there is very little involved with installing them, so they are usually treated as an after thought in the construction sequence. Switching to passive building adds a lot of new items that must be focused on early. "Everyone on the design team is used to ‘how we always do it’ so they’re not thinking about duct design and layout."
—Sloan Ritchie, Developer
"Occupant-wise, understand that many people don't like to tinker, preferring to "set it and forget it." For example:
Designing for natural ventilation and night-time cooling requires users to be aware of when and how to take advantage of opportunities, and then act on it. Without clear responsibility for such tasks, energy-saving opportunities can be missed.
Thermostats set to "auto" when a seasonal changeover between heating and cooling modes would likely be beneficial."
—Valley Waste Management design team
5. Verify your way through the construction process
"Mock-ups were part of the contractual requirements for crucial envelope details. This ensured the contractor to knew what to do before installing window installation and proper air barrier sealing. Mock-it up, review it, build it, review it."
—Valley Waste Management design team
"Using a blower door to test during construction can help identify minor leaks before they become major headaches. Testing air tightness after windows and doors are installed—perhaps before and after rough-ins by trades—can identify air leaks before insulation and drywall are installed. The point of the blower door is not really to test air tightness, as much as it is to find leaks by depressurizing the building, and listening for whistles."
—RMI Design Team
Pre-drywall blower door test is the best opportunity to find air barrier issues. Blower door test was the contractor's responsibility, as was achieving the PH air-changes per hour threshhold. Owner paid for the first test, contractor responsible to pay for subsequent re-testing if required.
—Valley Waste Management design team
6. Submetering can identify post-construction problems
By isolating loads at the meter box, RMI can see which systems are performing as expected—in regards to energy use—and which may need fine-tuning. Rather than look at a larger-than-expected energy bill and wonder where the problem is, granular submetering puts a spotlight on each system to ensure the building is operating as designed.
—RMI design team
7. Passive building improves many bottom lines
"The initial ‘sell’ to build through PHIUS+ was 100% financially driven. The company runs a tight ship financially (due in large part to outside constraints) and passive building certification was an existing, proven technology that could help them boost their level of care through lower construction costs and operational savings. The first building over delivers financially.
More importantly, the boarding house over delivers on other aspects that are key to the client’s mission: quality of life for the residents, innovation within their industry, and community leadership incorporating technological solutions that have positive environmental implications."
—Sam Rodell, Architect
8. It’s the little things
"When you take care of the big things, the little things get bigger. Parts of a design that used to be invisible become significant with high-performance construction. Even without attention to detail, the designers missed a simple little synergy mentioned earlier, about the heat pump water heaters and the computer servers working against each other.
That particular building is in cooling mode almost all the time—even in the winter—because of the body heat, and the computers, and things like water heating. It’s very hard to be intuitive about these things, and that’s one of the things I love about passive house, is that intuition has been replaced by physics.”
—Sam Rodell, Architect