As a Healthy Home Inspector, my friends and clients will often ask me what can they do to make their home healthier, or what is the healthiest home they can buy? When we think about Healthy Homes, a lot of different concepts are implicated – indoor air quality, toxic materials, mold and moisture issues, and electromagnetic radiation all come to mind. Some aspects of healthy housing involve occupant behavior or straightforward easy fixes. For example using nontoxic cleaning and personal care products, caulking around a bathtub, vacuuming more often, running exhaust fans or opening windows, and turning off a wifi router at night are all within the grasp of most residents. While these practices are great ideas to improve the overall health of a home, often the biggest impacts that a home will have on resident health are from the major systems involved with construction of the house. Many of these measures can be retrofitted into older homes or conventional built new houses, but the cost of the retrofit may put them out of reach for most renters. I will explore healthy housing solutions for renters in future posts, but in this post, we will explore five construction details that makes certain home stand out as being among the most healthy.

Top 5 Features of a Healthy House

1. All-Electric Heating, Hot Water, and Cooking– Nationally, there is a growing push for electrification of buildings – powering all of a building’s systems with electricity rather than fossil fuels like natural gas, propane, and oil. In Washington, 37% of homes use natural gas or propane for heating. In February 2021, Seattle was the first city in Washington to pass a natural gas ban for new construction, while other smaller cities like Bellingham are considering a gas ban. While the majority of proponents cite the climate benefits of having a future electric grid with more renewable electricity to power efficient heating systems and appliances, there are also a number of health and safety benefits of removing all combustion sources from inside a house. Burning natural gas and propane can produce a variety of harmful chemicals like carbon monoxide, formaldehyde, nitrogen dioxide, and ultrafine particles. The biggest health risk from natural gas and propane cooking and heating is that the products of combustion are not removed from the house – for example if a furnace or water heater backdrafts into the living space or if a range hood is ineffective at removing cooking effluent. Backdrafting is caused by negative pressure in the house that sucks contaminants back inside the house. It is typically checked during an energy audit or healthy home assessment, and can be corrected by improving the venting or introducing more makeup air to supply combustion.

While gas heaters and water heaters generally are code-required to be vented to the exterior, gas stoves are not directly vented and instead rely on a range hood to remove combustion products from the home. Oftentimes these range hoods are underpowered or overpowered and starved for make up air, or are so noisy that homeowners choose not to run them – all of which leads to an accumulation of combustion products into the house. This New Yorker article chronicles measuring the VOCs, nitrous oxide and particulate matter create over a typical Thanksgiving dinner on a gas stove, the air quality level in the house reached what would be considered “very unhealthy” levels where even healthy individuals are at risk of serious damage to the heart and lungs. Other studies have equated the risk to children from cooking on a gas stove with second hand cigarette smoke, finding that children in homes with natural gas stoves are 42% more likely to develop Asthma than those with electric stoves.

Today there are efficient electric heating, water heating and cooking appliances that exceed the performance of natural gas without the health impacts. Heating systems and water heaters that rely on heat pump technology are available for nearly all applications. For electric cooking, induction cooktops are emerging as the best technology. I would agree with the many chefs that cite the performance of gas stoves over conventional electric stoves as being a valid criticism, however based on my experience owning an induction cooktop in my house and campervan, I would argue that induction cooktops can perform better than gas stoves, without the harmful emissions. Madrona Building Solutions inspects gas appliances and provides recommendations for electric replacement equipment.

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Induction cooktop in my house

 

2. Balanced Ventilation System – Most homes rely on either passive ventilation (opening windows, leaks in building envelope) or exhaust ventilation (bath fans and range hoods) to provide fresh air and/or remove moisture, odors and contaminants from the house. The problem with passive ventilation relying on leaks in the building envelope is that it is largely uncontrolled (not feasible to control the amount of exterior air coming into the home or its pathway) and may introduce contaminants into the home (see air leakage below). Operable windows are a better solution but most homeowners don’t like to intentionally leave windows open in January for comfort reasons and there can also be a large spike in heating bills associated with this. Running bath fans and range hoods when showering or cooking is always a good idea, but especially in more airtight buildings, fans need to run regularly throughout the day to supply fresh air and many homeowners don’t run exhaust fans enough. The other issue with exhaust fans is that all the air that is expelled from the building needs to be replaced by makeup air and if the home is not air sealed well, some of this air could be running through a crawlspace or attic and introducing contaminants into the house.

The best solution is a balanced ventilation system that simultaneously exhausts stale air and supplies fresh air. Also known as air exchangers or an HRV or ERV, these systems will capture the heat from the waste stream and transfer it to prewarm the fresh air stream. This results in a more comfortable and efficient home that still has great air quality. As with heat pumps, there are an increasing range of products for all sorts of different applications from retrofits to new construction and from large homes to tiny homes. Ideally places where people spend the most time like bedrooms, home offices and living rooms should have a fresh air supply register in the room. Exhausts can be placed in areas where moisture is generated such as bathrooms or a laundry room, or placed in central areas like Hallways. Cooking appliances should have their own dedicated vent that vents to the exterior. Other considerations related to health with HRVs are making sure they are balanced (maintaining a neutral pressure in the home), run at the correct speed and time, and that they have adequate filtration of the air (ideally with MERV-13 filters or better).

HRV Design

                                                                              Typical heat recovery ventilator design

3. Self Adhered Water Resistant Barrier and Rain Screen – One of the key features of a healthy home is the damp Northwest is the ability to properly deal with rain and moisture. Ideally the exterior of the home should shed rain away from the building and allow moisture generated from inside to dry to the outside. As building science, codes and construction practices have progressed over the past decade, we now have a better understanding of how moisture can become trapped in exterior walls and lead to mold and rot. Two of the best practices for new construction or major remodels when siding are replaced are to install a self-adhered water resistant barrier (WRB) and to have a rain screen layer (air gap) between the siding and sheathing of the home to allow for water shedding and drying.  Rainscreens are now code required in British Columbia and Oregon. Modern WRBs can serve as both an air barrier to prevent air leakage and water barrier to prevent water intrusion while allowing moisture from inside to pass through to the outside. A self adhered WRB utilizes a peel and stick backing to attach to the sheathing whereas a mechanically attached WRB like Tyvek requires staples or nails.  When installed poorly (as is often the case) or subject to wind during construction, a mechanically fastened WRB will not serve it’s purpose and allow air and water to pass through. While there is somewhat of a cost premium associated with self adhered WRB’s, they are worth the peace of mind that come from knowing that the primary protection layer for your building’s walls will serve its purpose well.

Rain screens and WRBs are just two of the many components of the houses building envelope and drainage system. Roofs, gutters, flashing, windows, doors and soil grading all play a role in keeping your home dry and healthy. Madrona Building Solutions specializes in inspecting buildings for moisture issues and mold and applying principles of building science to both newer and older homes.

Shou Sugi Ban

Construction of my shop – the WRB is the blue layer, rain screen is the diagonal strips which separate the siding from the plywood sheathing.

4. Utilize Natural Building Materials – Using natural building materials is not that new of an idea. Adobe homes were built by indigenous peoples around the world before modern history and some still stand today including the so-called oldest home in the USA, in Santa Fe. Timber Framing first appeared in 200 BC and was one of the dominant construction types in the US until the advent of stick framing in the early 1900s. Straw bale homes first appeared in the 1890s and are still built today. However during the 20th century and particularly in homes built after World War II, manmade building products became the mainstream and offered builders a less labor-intensive and cheaper building materials. Drywall replaced lathe and plaster, plywood and OSB made from glued wood fragments replaced dimensional lumber sheathing boards, vinyl and fiber cement siding replaced wood siding, and carpet and engineered wood floors became more common. Some materials that were introduced later were discovered to be toxic and subsequently banned, such as lead in paint and plumbing systems and asbestos in siding, flooring, ceilings, and insulation. Other toxic building materials are still in use today (see ILFI’s Red List ) for an up to date listing.

Given the increasing awareness of toxicity in building materials, many consumers are starting to demand healthier products and more transparency. Utilizing building products that are closest to their natural state, is the best way to ensure that there are no harmful chemicals in the product. Many of these natural products also have the advantage of lower embodied carbon emissions. To maximize health benefits, focus on natural products on the interior first, where offgassing chemicals are the biggest concern. Some examples:

  • Chose zero-VOC paints and finishes, or better yet opt for a natural finish like clay-based paint, linseed oil and beeswax polishes
  • Opt for natural hard surface flooring products like hardwood, cork, linoleum/marmoleum, tile or polished concrete slab over vinyl/laminate, wall-to-wall carpet or engineered wood/bamboo floors. If you would like a softer floor, consider a wool area rug.
  • Chose solid wood cabinets, trim and furniture over engineered wood products

    Hardwood Flooring

5. Maximize Daylighting and Choose Human-Centric Artificial Lighting –  As humans, our bodies operate on 24 hour cycles primarily driven by lighting levels and color temperature known as circadian rhythms. The circadian rhythm can affect many processes in the body such as hormone release, digestion, and body temperature, but its primary affect is on our sleep patterns. The best form of lighting homes for health is sunlight and appropriate use of windows, skylights, and/or light tubes can bring in ample daylight levels. However, too much glazing can cause issues with overheating, heat loss and glare, so daylighting calculations should be performed in new construction/remodel scenarios. Modern building codes require a minimum amount of windows but many older houses I’ve been into lack enough windows for proper daylighting.

When it comes to artificial lighting, the main goal for healthy benefits is to imitate the light cycle of the sun. Humancentric lighting follows a holistic approach that includes all aspects of how lighting affects occupant wellbeing, productivity and comfort in the built environment. In the morning, bright sunlight tells our biological clock that the day has begun and certain bodily functions can be activated. To achieve this with artificial lighting, blue spectrum lighting (>4000 Kelvin) can be like a cup of coffee in terms of increasing concentration and alertness. Blue lighting is great for offices, schools and commercial building where the building is occupied during daytime hours. While most people prefer warmer colors in their homes, you could selectively add cooler colored bulbs to areas where you spend time in the morning or try adding a tunable task light to your desk. In the evening around sunset, it is important to avoid blue spectrum lighting and shift to warm white lighting to help our body produce melatonin for better sleep. Avoiding the use of electronics with screens 2 hours before bed can help, as well as blue-light blocking glasses and lightbulbs.