Healthy and Comfortable

Airtight and well-insulated buildings are quieter and maintain consistent indoor temperature more easily. Air leakage or air infiltration allows unheated or uncooled air, depending on the season, to enter your home through unwanted or unseen gaps and the air you’ve paid for to heat or cool to escape. Airtightness is the degree of air leakage or air infiltration a building has. Airtightness eliminates unpleasant drafts in your home. For information on natural monolithic wall construction, e.g. adobe, rammed earth, etc., see “Building Systems, Natural Materials and Green Innovation” below.

The basic principles of an airtight building are installing well-sealed windows and doors, minimizing penetrations in walls and ceilings, and sealing air movement at joints in framing. Replacing uncontrolled air infiltration with mechanical heat recovery ventilation allows for more fresh air in the building without losing or gaining as much heat as uncontrolled air infiltration.

Insulation provides resistance to heat flows, allowing a building to better maintain indoor temperatures. An insulation material’s effectiveness is determined and measured by its thermal resistance, also known as R-Value. Insulating a building to achieve high R-values can reduce the building’s heating and cooling load while also allowing it to be more comfortable. It also dampens the amount of sound from outside, making the building quieter. Buildings are typically only insulated once in their lifetimes, adding a high degree of insulation will pay dividends for years to come in increased comfort and lower energy costs. When considering insulation and costs, the shape and form factor of your building can have a big impact. The compactness of a building or the ratio of the external surface area and the internal volume of a building, has a considerable influence on overall energy use.

The change to the ratio of external surface area to internal volume requires additional insulation to maintain the same efficiency. In addition to increasing the insulation required, a building with a more complex form is likely to have a higher proportion of thermal bridges. Thermal bridging happens when a material (or lack thereof) within a wall’s structure that allows a faster than normal rate of heat transfer, like the 2×6 studs in a wall that sit between the insulation. In addition to the shape of a building, strategies like a layer of continuous insulation on the outside can reduce thermal bridging. Adding exterior insulation or radiant barriers to the roof helps stop heat from entering the building. A well-insulated building can greatly reduce, and possibly eliminate, the need for mechanical heating and cooling, further reducing building and operating costs. Source

Designing a building so that the rooms that are used most during the day face south means they will get light and heat from the sun, reducing the need for mechanical heating systems and electrical lighting, making them more pleasant and comfortable. During the summer, appropriate shading can reduce the amount of solar heat gain when the sun is highest in the sky. Designing your roof for southern exposure also maximizes the energy generation capacity of any future rooftop photovoltaic installation (i.e., rooftop solar). Orientation can also be advantageous to capture prevailing winds for cross-ventilation. Strategic orientation in conjunction with natural building assemblies can greatly reduce, and possibly eliminate, the need for mechanical heating and cooling, further reducing building and operating costs.

Windows can make up a significant portion of your building construction budget but do many jobs: let in natural light and views, bring in fresh breezes, eliminate drafts and insulate. Choosing high-performance windows and the number and sizes of windows are fundamental parts of your energy design. Triple pane windows reduce heat loss or gain through the window and increase the surface temperature of the inner pane, which reduces the sensation of cold drafts, and provide fire resistance. If budgets can support investing on glazing, it is recommended to invest in tempered exterior panes, which aligns with wildland urban interface code requirements as it aids in preventing windows from breaking during fires from external direct flame contact, radiant heat, or embers ignitions, in turn protecting the interior of the structure.

Most conventional buildings have no mechanical ventilation besides a bathroom fan or kitchen hood, which are only run intermittently. Without regular outdoor air ventilation, the concentration of pollutants inside the building can easily rise above EPA air quality standards, particularly when using natural gas appliances. Heat recovery ventilation or energy recovery ventilation provides fresh filtered air by passing outgoing and incoming air through a heat exchanger which brings the fresh incoming air closer to the temperature of the outgoing air. This efficient and controlled means of providing fresh air to a building allows you to increase the amount of fresh air coming in or shut it off entirely if there is smoke or a bad air quality day. You can’t do either of those things with uncontrolled air infiltration. Lastly, air filters (e.g., MERV 13, HEPA) are especially important if homes are near major thoroughfares or in a region prone to wildfire smoke and/or poor air quality.

Windows can make up a significant portion of your building construction budget but do many jobs: let in natural light and views, bring in fresh breezes, eliminate drafts and insulate. Choosing high-performance windows and the number and sizes of windows are fundamental parts of your energy design. Triple pane windows reduce heat loss or gain through the window and increase the surface temperature of the inner pane, which reduces the sensation of cold drafts, and provide fire resistance. If budgets can support investing on glazing, it is recommended to invest in tempered exterior panes, which aligns with wildland urban interface code requirements as it aids in preventing windows from breaking during fires from external direct flame contact, radiant heat, or embers ignitions, in turn protecting the interior of the structure.

Natural gas (methane gas) appliances leak methane into a building (Sources 1, 2). Burning gas creates harmful pollutants like formaldehyde, nitrogen dioxide, acetaldehyde, and ultrafine particles in, and according to several studies, leads to a higher risk of asthma vs. an all-electric building. Burning gas for heating also creates risks from carbon monoxide poisoning and gas explosions. All-electric buildings with induction/electric ranges and efficient electric heat pump heating and cooling systems, and electric heat pump water heaters offer improved indoor air quality and eliminate carbon monoxide and other health safety risks. A well-designed heat pump system can also lead to better distribution of heating and cooling and improved overall comfort. Similarly, cooking on an induction range is faster, more precise and more efficient than on traditional gas or electric ranges.

Many construction materials, wall/floor coatings, and furnishings contain volatile organic compounds (VOCs). VOCs include a variety of chemicals, some of which may have short- and long-term adverse health effects. Concentrations of many VOCs are consistently higher indoors (up to ten times higher) than outdoors. VOCs are emitted by a wide array of products, numbering in the thousands. Choosing construction materials and furnishings that are low in VOCs and having a heat recovery ventilator to bring in fresh outdoor air can limit your exposure to VOCs. To further avoid poor air quality, it is recommended to avoid PVS (including paint), vinyl (including windows and simulated materials), foams, formaldehyde, fire retardants, and antimicrobial finishes. Choosing renewable natural or minimally processed materials wherever possible will improve the interior environment and also help mitigate risk of pollution for the exterior environment if there is another natural disaster. Lastly, consideration of a product’s lifecycle matters for our regional sustainability and climate action goals, such as reducing climate changing pollution as a result of manufacturing processes and transportation.

To learn more about options for air purification, heat pumps, efficient and all-electric appliances, natural building materials, and prefabricated building approaches see the US Green Building Council, California’s California Wildfire Rebuilding Guide, pages 52-59.