MOST AIR EXCHANGERS/HRV’s DON’T WORK
INDUSTRY HAS IT WRONG
The above photo shows a fresh air intake for a typical residential air exchanger/heat recovery ventilator. It is obviously clogged even though this is a relatively new house that was put up for sale. Industry is failing the consumer because these fresh air intakes don’t work, they get contaminated too easily because the inlet screen has large openings [typically 1/4 by 1/4] and all sorts of insects and particles fly through. The interior connecting duct is typically corrugated plastic that can never be properly cleaned.
Before reading this post please take note of the following “…. Lung malignancies account for 4 out of every 10 Canadians who die from cancer” in other words it is the number one cancer killer. “40.5% of all cancer deaths in Canada are a result of lung malignancies, despite the fact that many patients were non-smokers” [ref. Current Oncology, Patafio et al., Queen’s University research, excerpt from the National Post, May 13,2016 ].
Nothing is as important to your health as the air you breathe. We breathe in oxygen and exhale carbon dioxide. Fresh outside air is considered to be synonymous with oxygen. The lungs of children are smaller than adults so they are the first to be affected by poor air quality. The most important aspect of air quality is fresh air/oxygen. When you go to the emergency room of a hospital, a nurse is likely to greet you at the time of admission, even before you get to be examined by a doctor. The nurse will slip a type of cover over your index finger to measure the oxygen content of your blood. The purpose of doing it is to determine whether or not your immune system is functioning properly. If a person has been breathing bad air for some time, their immune system is likely to be feeble; there resistance is likely to be down. You’re less likely to be capable of resisting common types of infections, more likely to be extra sensitive to various toxins in the environment.
The National Building Code in 1995 recognized the importance of fresh air to one’s health. It tried to put an end to the myth that Canadians could rely on “natural ventilation” by opening windows to supply the needed fresh air. They explained the obvious that windows were hardly ever opened because of inclement weather, our winters are too cold and our summers are too hot and humid. The regulation then called for a complete mechanical air change in the whole house, with fresh air delivered to each and every inhabited room, to be accomplished within 3 to 4 hours. There is a 10 year delay before the National Building Code gets adapted within each province as part of their Construction Code and subsequently modified and adapted within each municipality. Municipalities are currently in the process of adapting the 2010 National Building Code. The regulation regarding mechanical air changes to provide fresh air took extra-long to be adopted and is still not being properly implemented. In Québec, the regulation was interpreted to mean that air exchangers/heat recovery ventilators should be installed in new construction. As someone who has been doing building inspections for 50 years, I have never seen an industry respond so poorly to a code requirement. Air exchangers don’t work well. The intake for the supply air has a grill [pictured above] with quarter inch by quarter inch openings so that dust, insects and even grass cuttings get sucked in to the flexible corrugated inlet pipe which one is unable to ever clean. That air then moves to a small air handler where an attempt is made to transfer some of the energy from the exhausting interior air to the incoming air. The problem is that these units become easily contaminated and they are not being properly maintained [everyone is too busy working, living their lives]. The worst problem is that they do not deliver a sufficient amount of fresh air.
The amount of fresh air which is supposed to be delivered stems from an American standard. The US standard for ventilation is described in ASHRAE’s handbook [The American Society of Heating, refrigerating and Air-Conditioning Engineers, Inc.] 62.2. For every occupant you need 7.5 cfm [ft.³ per minute] of fresh air +1cfm per hundred square feet of floor space. For example, a 3000 ft.² house with a family of four would need 60 ft.³ of fresh air per minute. That’s a lot of ventilation. Very few houses come close to that kind of standard. Most houses I get to inspect still don’t have any mechanical air changes. The most popular type of air conditioning today is a split system with a compressor/condenser on the outside the size of a suitcase, connected to the interior wall-mounted air handler only by refrigerant piping. That involves no air change whatsoever. In North America we have apartment buildings which do have air changes thanks to the fire regulation intended to prevent smoke migration in corridors. Rooftop units deliver fresh air to corridors in order to pressurize them to prevent smoke migration and the fresh air from those corridors is then transferred into the interior of apartments where it gets to be expelled through kitchen hood, bathroom and clothes dryer exhausts. When the right amount of air is being delivered, an ordinary person should be able to smell the difference. Everyone knows what fresh air smells like. If kitchen cooking smells, the smell from a neighbors barbecue or body odours dominate then you are not getting a sufficient amount of air change. Some mechanical engineers pretend it is too difficult to assess. I have been using carbon dioxide detectors for more than 30 years. They are easy to use and you will know immediately whether or not air changes are taking place with fresh air.
All systems have their limitations and even new apartment buildings sometimes fail to deliver the required amount of fresh air. One of the most egregious cases I had last year involved a single parent with a serious respiratory problem who was on a waiting list for a decade or so to get into social housing with proper accommodation. She moved into a new apartment building in Montréal’s plateau district built exclusively for social housing candidates. To her horror she discovered that all the occupants in the building, most of whom are on welfare, smoked continuously. She was on the top floor of the building and cigarette smoke prevailed near all the interior exhausts [kitchen hood, and bathrooms] even at the exterior balconies. The WHO [World Health Organization] recommends that no smoking be permitted in social housing and, in fact, it isn’t in most western countries.
After oxygen, the next most important aspect of good quality air should be the elimination of all microscopic particles that are less than 2.4 µ [microns]. That is because particles of that size can get into your lungs and your bloodstream. In the US, the EPA [Environmental Protection Agency] has established the 2.4 law to try and control that kind of pollution. There is equipment available that can measure and count microscopic particles suspended in the air. One is able to find where those particles are coming from. However, the approach taken by air-quality specialists gives all the emphasis to the determination of the types of toxins in the air especially if they can lead to morbidity. For them, it is not enough just to establish the presence of microscopic particles, they want to grow cultures and know the type, compared to outside conditions etc. That requires the work of a laboratory. Concentrating only on toxins that can lead to morbidity is, in my opinion, limiting. If one considers having a healthy environment as a preventative measure, then it is more important to be checking for basic air quality such as fresh air and the presence and elimination of particles less than 2.4 µ in as many houses as possible. For example, it should be done at every house that gets purchased [e.g. at the time of a pre-purchase inspection]. The highest calling of a professional should be to help ordinary people to lead healthy lives.
There isn’t enough acknowledgment of the importance of human factors that create contamination. For example, having had the responsibility of decontaminating an apartment building in the Côte des Neiges area of Montréal, I found that Santé Quebec was too ready to blame the architecture rather than the occupants. The city authorities on the other hand, did recognize the importance of educating or acclimatizing the occupants to the architecture and its limitations. The building had been around since the 50s. It had already proven itself over the years, having provided relatively good accommodation. Basically it was the infrastructure that needed upgrading. The way the occupants were living made the air-quality exceptionally bad. There was serious overcrowding [not enough fresh air for the occupants], over furnishing – too much stuff piled up against outside walls [heat or air is unable to circulate at the walls leading to condensation], not making use of kitchen exhaust hoods or bathroom exhaust fans or taking out garbage on a timely basis because cooking smells and warmer climates relate to their places of origin [leads to fungal growth, cockroaches etc.], having too many plants, aquariums or pets especially cats [leads to fungal growth, mold spores, cat allergens – particles between 0.1 and 5 µ] etc..