Dan Thiede live-blogs this session at the Minnesota Green Communities third annual statewide GREEN BY DESIGN Conference. View all conference presentations here.
Presenter: Pat Huelman, University of Minnesota Cold Climate Housing Program
Pat tells us how—if we can sharpen our pencil of building science, and better engineer—we can get better building performance while spending less money.
View the presentation from this session
Good & Bad News
There is good news. We have great houses—some of the best in the country—but we are not where we could be in terms of our climate, our economy, and the environment. Also, we are finally talking about efficiency and renewables, but we are not doing enough. We have the knowledge to create more efficienct, durable, healthier, and environmentally-sensitive homes, but we have been focused on incremental change, and the actual progress is not that impressive. We can spend less and be more green!
Building Science Principles
Key building science principles:
- Heat goes from warm to cold
- Water vapor goes from more to less
- Water vapor goes from warm to cold
- Air-in must equal air-out (and visa versa)
- Air must have pressure and a path to flow
- Drain the rain (and the soil)
- Most of the action is at the surfaces
- Gas concentrations (pollutants, water vapor, etc.) is a function of source strength and removal rate
Ten Key Components that are the backbone for the systems approach in Minnesota homes
Adhering to these components will assure that a house is efficient, healthy, and durable. A newly constructed cold climate house should have:
- Thermal insulation over the entire building envelope, including the foundation. This is usually a combination of materials. It should be installed to minimize gaps and cracks.
- A continuous air barrier on the warm side of the building envelope. This barrier is essential to hold in the warmed (or cooled) air and prevent moist air from entering the structural cavities where it can condense on building materials such as the outside sheathing.
- A vapor retarder on the warm side of the building. This is to keep the insulation and structural cavities dry.
- A continuous weather barrier on the exterior of the building. This is needed to prevent water and wind from blowing into the wall cavity where it can cause mold and mildew problems, and reduce the effectiveness of the thermal insulation.
- Energy-efficient, condensation resistant windows. These windows should include a newer technology called “warm edge technology.” It helps keep the edges of the window warm to reduce condensation.
- Effective ground moisture/soil gas control. Many of the moisture problems in today’s homes result from moisture coming through the basement walls and floor. There are several ways this can be controlled with good waterproofing and a drainage system.
- Low-toxicity materials, finishes, and furnishings. Choosing materials and furnishings carefully can help avoid indoor air quality problems and make the home healthier.
- Safe, efficient heating and cooling systems. Direct-vent and sealed combustion equipment will greatly lower the risk of pollutants such as carbon monoxide from getting into the house when the furnace and hot water heater are in use.
- Mechanical ventilation. A carefully planned and installed ventilation system is critical to assure good indoor air quality. There are many options available to remove stale air and bring in fresher outdoor air.
- Efficient and safe appliances and lighting. Appliances and lighting are important parts of the system. They should be carefully chosen to complement the rest of the system.
Heat, Air & Moisture (HAM): In the end, heat, air, and moisture flows will drive the performance of the system. That means that heat transfer (energy), indoor air quality, and moisture are the three most important things to think about when it comes to building performance. There are ten key compontents, which you can see on Pat’s presentation on the Green by Design website when it is made available next week.
A Systems Approach
We need to stop looking at buildings in their parts, and start looking at the entire building and all of the interrelated systems in that building. This is where we will get real performance delivery. There is a huge difference between a building full of green products and a green building. We also need to avoid greenwashing, green noise, green glazing, and move toward deep green. We also need to know which actions will make a significant and lasting impact—we need to know the magnitude of our actions. We need to prioritize those actions that lead to to larger and more certain benefits.
We know how to reduce energy use and make heating more efficient, but it does not show up in the building performance data over the last half century. Even where we have improved, as with heating efficiency, we now pay more because we are building bigger homes. We have used better products, but we have not thought about how they all need to work together. Poor energy design, insulation, and installation are also to blame. Whenever we are going to choose to build, we have to ask: (1) Did I save energy?; (2) Did I save money?; (3) Did I save the environment?
Space Heating
- Insulation performance (space, thermal bridges)
- HVAC efficiency (size, installation, testing, ductwork
- Efficient windows (number, direction, air and water)
- Air flow management (ventilate right and build tight)
Bottom Line
- We must move from product to process to performance
- You can’t spell GREEN without EE (energy efficiency)
- The proof is in the performance
- We need designs and models that are robust enough to lead to a systems approach
Robust vs. Fragile Building Features
In your foundations, walls, houses, ductwork, etc. opt not for what is initially cheaper and always done, but for what will be the most robust and resiliant in the long haul.
Fragile designs include: tuck-under garages and bonus rooms over the garage, challenging roof and roof/wall connections, cantilevered floors, and upper-level laundry rooms, interior foundation insulation, ductwork outside the thermal envelope, vented crawlspaces, carpet on slabs—especially below grade.
Robust designs include: simple house geometry, simple roof geometry, passive solar design, detached garage, exterior foundation insulation, comprehensive and tested air sealing, vented attics, low-sone spot ventilation, blown-in high density wall insulation, vented rain screen, open web floor trusses, foundation waterproofing with drainage, central exhaust systems, warm-edge windows.
