In our last blog about indoor air quality (IAQ), we discussed what influences IAQ, what effects it has on humans and nature, and how to create healthier IAQ in your home.
As a recap, IAQ is measured by the quantity and type of pollutants in the air within a building. The pollutants that decrease the IAQ (make the quality worse) can be anything from biological pollutants such as mold and mildew, bacteria, dust or pollen, to carbon monoxide or volatile organic compounds (VOC’s)4. These pollutants can cause a wide variety of health problems for humans and animals, from mild skin irritations all the way to damaging internal organs and causing cancer.2,5
While ventilation is just one of the many factors that affect IAQ mentioned in our previous blog, it is a multifaceted topic and requires a deeper dive than we were able to give.
We’ve already established that healthy IAQ is important, but how does ventilation impact it and what are the current shortcomings of code-standard ventilation systems?
Firstly, IAQ can be 2-5 times more polluted than outdoor air quality6; therefore, it is vital to expel a greater quantity of indoor air and intake more outdoor air to increase a building’s overall IAQ.
However, not all ventilation systems are made equally. Often, with forced air-heating and traditional air-conditioning systems, the main method of ventilation is infiltration or purely natural ventilation (opening windows)3.
This is problematic, because there will not be a great enough flow of air to expel the polluted indoor air and the outdoor air comes into the building’s envelope untreated. While outdoor air is generally less polluted than indoor air, it would be counterproductive to bring in smoky, smoggy or pollen filled air, for example, and should still be filtered before entering the building.
When mechanical ventilation is installed in a simply code-standard building, the typical system must be manually turned on and off and doesn’t have the capacity for higher airflows or continual airflows. For this reason, conscious builders like TC Legend Homes go above and beyond the less-than-optimal code-standard systems and always uses a Heat Recovery Ventilator (HRV).
HRV units allow for continual filtered airflow. They are also capable of utilizing smart technology with sensors to detect CO2 and humidity within the house, allowing the system to automatically adjust air flow.
The humidity tracking and management is a huge advantage because it creates a more comfortable environment to people, pets and indoor plants alike and helps keep mold and mildew growth in check. On top of increasing airflow and managing humidity, the HRV also contains HEPA air filters to ensure the incoming air is stripped of as many pollutants as possible.
Of course, the extra benefit to these systems beyond increased IAQ is that they “recover up to 90% of the heat and contribute to an energy savings of up to 50%.”1
This means HRV systems save money by lowering the overall energy bill, as well as decrease the building’s carbon footprint by using energy more consciously resulting in less consumption of energy, fossil fuels and other precious materials.
In all, choosing the best ventilation system can mean creating a healthier home, as well as reducing your wasted energy consumption and having a lesser impact on the environment.
2“Biological Pollutants’ Impact on Indoor Air Quality.” United States Environmental Protection Agency (EPA), EPA.gov, https://www.epa.gov/indoor-air-quality-iaq/biological-pollutants-impact-indoor-air-quality. 2/10/2022.
5“Volatile Organic Compounds’ Impact on Indoor Air Quality.” United States Environmental Protection Agency (EPA), EPA.gov, https://www.epa.gov/indoor-air-quality-iaq/volatile-organic-compounds-impact-indoor-air-quality. 2/10/2022.
SIPs are wall, roof (and sometimes floor) panels. Fabricated from a slab of foam sandwiched between two plywood sheets. Actually, it’s not ply it’s OSB (oriented strand board).
The sandwich-panels can be up to 24’x8’ and are made in the SIPs factory, in our case Premiere-SIPs in Puyallup. The doors and windows are cut-out in the factory, a stack of pre-fabricated house panels are loaded onto a trailer and arrives on-site where the SIPs are assembled… a bit like Legos.
Because TC Legend Builds affordable Net Zero energy houses, we use our crew to assemble the wall panels, man-handling them into place, but a crane can be used for walls. We do use the crane to set to thicker, heavier roof panels.
Our goal with SIPs panels is to create a continuous foam box, surrounding the inside of the home. When you remember that there’s 4” foam under the concrete slab, the 6” foam walls and 10” foam roof trap all the heat inside the house.
The ‘S” in ‘SIP’ stands for structural and the panel-system carries the load of the house, floors and roof, and does not need the sticks of vertical lumber you see in the walls of a conventionally framed house.
How are SIP panels joined? We’ll use the walls as an example:
The SIPs panels typically have the interior foam held-back to form a 1.5” gap at the panel edges. Two panels are joined by setting a ‘spline’ into the recessed gap on one panel, then sliding the second panel over the spline, nailing the connecting spline in place through all four edges. Splines can be made of 2×6 lumber (L-spline), foam mini-SIPs (called S-splines), or an insulated TJI spline (called an I-spline).
Because a 2×6 lumber splines touches both the warm inside of the house wall, and the cold exterior of the house wall, they are said to cold-bridge. A cold-bridge creates a poorly insulated pathway for the warm inside energy to travel to the cold exterior. There a many cold-bridges in conventional framing and that’s why we don’t do it. We aim to minimize L-splines as they have an insulating value of R7.8, compared to R29 for our Neopor graphite foam 6.5” Premiere SIPs wall panels.
Last week the TC Legend Homes crew finished off the SIPs roof structure on the Lake Stevens house.
On average we take about (2) days to assemble the 1st floor SIP wall panels. We build the 2nd floor-level TJI and sheeting floor system over the succeeding (2) days. The upper level walls take a day or so, and then it’s roof-day!
On roof-day the crane arrives early, and the roof panels are rigged, swung up, and screwed in-place by Ted and Norm. The crew have pre-assembled the boundary supports, so we don’t use more crane time and belch more diesel than necessary. The boundary support is a continuous 2×10 that seats into the 1.5” perimeter recess & connects together the outside edge of the roof panels.
SIPs are very fast to assemble and incur almost no waste material onsite because everything arrives pre-cut. Most excess off-cut foam is recycled back into the process during factory fabrication and the Premiere software nests the required panel shapes for maximum efficiency, making Premiere more streamlined, more profitable and more environmentally responsible.
Air sealing is very, very important for energy efficiency.
Imagine a fast, cold wind blowing over the building and all the warm air streaming out through the construction cracks. The Lake Stevens house is modeled to need a maximum of 12,500Btu/ hour to heat in midwinter, if we air-sealed the envelope to 0.6 air-changes per hour. (Note: (1) air-change-per hour assumes the entire volume of the house has the air replaced once within (1) hour).
If we air-sealed the Lake Stevens house to 5.0 air changes per hour, code minimum, we’d need 19,000Btu/h of heating for midwinter! So you can see that air sealing to reduce the air-changes per hour can give over 35% reduction in heating load.
SIPs are a pre-sealed sandwich, and compared to typical construction there are far fewer construction-joints in a SIPs building due to the large SIPs panel size. The standard SIPs assembly process includes installing beads of specialist mastic to air-seal and adhere the panels to each-other. SIPs have a measurable dollar advantage with that high level of pre-sealing and easy panel-to-panel air sealing. Meaning you can buy and run a smaller heat pump. And we haven’t yet examined the standard R29 insulation in the equivalent 2×6 wall!
Here at TC Legend Homes, we are excited to ring in the New Year! We kept busy in 2018, but we were not as active as we would have liked in keeping our “fans” updated on our recent projects. So, while we’re committing ourselves to doing better in the future, this post is an attempt at bringing everyone up to speed on some of the happenings of 2018 in a (relatively) short summary:
One home completion (started in 2017) in Seattle.
Four complete home builds; two in Bellingham, one in Redmond, and one in North Bend.
Construction initiation on two ADUs; one in Sumas, and one in Bellingham.
All projects were Built Green 5-Star Certified, EPA Indoor airPLUS certified, and met DOE standards as Zero-Energy Ready Homes.
Ted presented at the Built Green Conference 2018 in Seattle. He shared the podium with homeowners Andri Kofmehl and Veena Prasad. Their topic, Bridging Innovation and Affordability: How to Build the Greenest House Possible Without Compromising on Aesthetics or Breaking the Bank, featured our 2017 Emerald Star home. More details on this can be found at this link to our portfolio.
Craig and Thad did a little San Diego couch surfing to attend a Builder’s Round Table, composed entirely of 2018 Department of Energy Housing Innovation Award Winners, where we learned a little about the future of high-performance building.
We participated in the Whatcom County Showcase of Homes, featuring the second home shown above – a great example of an affordable net-positive home in Bellingham. You can also read more about it in our portfolio.
Ted and Thad spoke at the Northwest EcoBuilding Guild’s annual Green Building Slam about how building net-positive can actually make it easier to afford more home while preserving quality of life.
We “expanded” our business operations into a SIPs Tiny Office (above).
Ted wrapped up his speaking engagements in December, at the Sustainable Connections Green Building Slam, with a talk about why we need to embrace sustainable building – because Our Kids are Going to Need a Place to Live.
Our newest project is almost complete! These homes were designed to be sustainable without compromising the luxury one expects in high-end building. Located in central Columbia City, the homes are just two blocks from the the core shopping and restaurant area and just three blocks from the light rail station, earning a Walk Score in the 90s. The homes’ many windows offer views of Mt. Rainier and the Cascades.
2,250 square feet
All heated floors
Triple Pane Windows
Stainless Steel Appliances
In-House Air Filtration System
Electric Car Charging
9 Foot Ceilings
These positive-energy homes use non-carbon-based sources of energy to produce 100% of energy needs for appliances, heating, and lighting. Additionally, the homes generate enough energy to power an electric car. This means no utility bills or additional charges to operate your electric car. And, most importantly, a positive-energy home does not produce carbon emissions, which are responsible for global warming. Living in a positive-energy home is one way of “doing your part” to ensure continued habitability of our planet.
Visit the links below to follow the building process and learn more about how these custom-designed homes incorporate the latest technology to ensure the highest levels of energy efficiency and quality.