How do you define high performance? If you build to code and accidently end up with a super tight enclosure, are you high performance? (I’ve tested a code-built house that ended up at .33ACH50.) Or do you need to build above code in all four of the control layers, water, air, vapor and thermal to reach the high-performance accolades? To tell you the truth, I don’t particularly like the term high performance. If you are shooting for a certification, then you are building to “Zero Energy” or to “Passive House” or whatever model you are trying to achieve. If you are not going for a certification, then you are simply building above code, or building better, but for clarity with this blog post, we’ll call it high performance.
To be considered high performance, a building must clear several hurdles, at least in my opinion. The following are what I feel are the requisites of performance.
A well designed and executed water control strategy. The water control layer is the most important of the control layers, after all, if it gets wet and can’t dry, then the structure will have a short life span. The key is a properly installed water resistive barrier with at least a draining rainscreen. Even better, a draining and drying (venting) rainscreen.
Test the water control layer. What, how do you test that? Well, with water. Flood the windows and walls with water from a garden hose. Get them wetter than what you ever expect them to see once they are in service. Even better, put the home under a negative pressure, (using a blower door) then flood the walls and windows. If they don’t leak under this extreme event, you’re good to go, at least until the window manufacturer’s warranty runs out.
A well designed and executed air control layer. Air control starts in the design of the structure, if you cannot execute a red line test around a section drawing of the building, then you need to go back to the drawing board. (A red line test is outlining the air control layer of an architectural section drawing using a red pen, if the pen leaves the paper, air control is not continuous. Follow Steven Baczek on the Build Show Network for more details on the red line test.) Installing the layer effectively and continuously is also a requirement.
Confirming the continuity of the air control layer. How did you do with the installation of the air barrier? The only way to know is to test, trust but verify! If you have an aggressive metric to hit, say less than 1 ACH50, you will want to test at least twice, if not more. If you are new to building tight, definitely perform a mid-build test. Corrections are a lot easier before the wall and ceiling finishes are installed.
Think about your vapor control strategy. Are you getting the theme here, I’m stressing the control layers in order, and even though the vapor control layer is the #3 most important, if you do well on designing and executing the air and thermal control layers, vapor usually becomes much less of a concern. But still, give it some thought!
Design with extra insulation in mind. The beauty of extra insulation, especially on the exterior, building components can stay warmer and therefore, stay dryer. Extra attic insulation may result in a lower risk of ice dams, and foundation insulation is critical for keeping foundations warm and dryer. A lot of people look to insulation as a way to save money but keeping building components warmer results in things also staying dryer, longevity!
Tell your HVAC contractor your plans. All these performance upgrades cost extra. You’re going through the effort to build a better, more efficient, and longer lasting home. A way to offset some of the costs is by installing smaller heating and cooling equipment, but this will only happen if the people bidding and installing the equipment are aware that you are reducing the heating and cooling requirements. You might also want to consider hiring a third party to size and possibly design the HVAC systems.
Install a balanced mechanical ventilation system. Building better has a side effect in cold climates, increased interior moisture and decreased indoor air quality. The nice thing is you now have the ability to control the amount of air entering and exiting the building. This is where energy recovery ventilators (ERV) and heat recovery ventilators (HRV) shine. One piece of equipment to exchange inside air with outside air and transfer some of the heat that would otherwise be lost. The ERV may also transfer some of the moisture that would normally also be lost. Try doing that with a home that relies on natural air leaks for its fresh air. *Some areas of the country may also benefit from a central dehumidifier.
Choose better windows. I have had several conversations with homeowners who have been talked out of installing triple pane windows by their local lumberyard salesperson. They’ve been told there is no payback in energy cost savings. Energy savings is a small part of choosing better windows. What’s more important to me in my climate is condensation control and window longevity. With improvements in the building shell, a home can handle a higher interior humidity level, as long as the windows aren’t the weak point, the dehumidifier in the home. With triple pane windows, the interior pane stays warmer, even in my extremely cold climate, resulting in less of a chance of moisture and ice accumulations.
Train the homeowner. I have been in so many new homes where the homeowner has no idea how some of the equipment works. One of the homes had a 15-year-old HRV that had never been serviced, I suggested calling an HVAC professional to clean and tune the unit, I know I wasn’t going to open it. I’ve also been in homes where the heat and air conditioning were running at the same time. Don’t assume the homeowner knows, it’s been my experience that often they don’t have a good understanding of how buildings work.
Return to past jobs to learn and make improvements in your craft. Most homeowners will be thrilled to visit with the person they spent several months to several years working with. You will be able to find out if the home is meeting their expectations. Are they comfortable, are there any complaints? Inspect the windows and doors, open the ERV or HRV along with the other HVAC equipment, has it been cleaned recently? Take a walk around the home, what’s lasting, what needs maintenance, what is failing? You can learn so much from a simple visit to a friend you haven’t seen in a while, (both the house and its owner).
There you have it, my
ten eleven opinions on how to build better. What did I miss? What is important to you? Please share your thoughts. Before you do, I have one final suggestion.