I’ve often felt that most renovations are a compromise in efficiency, but when it comes to getting fresh air, everyone drops the ball. From the homeowner pleading ignorance, the builder, the mechanical designer, the municipal plans examiner and the building inspector, each having their own agenda; ventilation systems need more attention as homeowners pay the price in diminished health or loss of cognitive function. We love fresh, clear, clean water piped through our buildings, but for some reason, fresh air gets ignored by the designers, the renovators and municipal plans examiners. The air in your house deserves to be as fresh and clean as your drinking water; now pay attention!
The Washington Post’s Chris Mooney reported last year about “…a study published Monday reports that workers showed significantly lowered cognitive functioning after spending a day in a simulated office environment featuring high [typical] concentrations of carbon dioxide and volatile organic compounds. By contrast, in conditions set to simulate a… building with enhanced ventilation — cognitive performance was higher.” Lead researcher Joseph Allen at Harvard said the results in increased cognitive function were “Shockingly higher.”
Some histrionics for perspective on the ventilation issue are needed. A new home’s design and construction processes are bound to follow the Ontario Building Code (OBC), but renovations of existing building don’t. The OBC is not retroactive and doesn’t compel the home owner to upgrade the existing building shell or mechanical systems to meet OBC requirements – they could if they wanted to. So at best the builder not wanting to charge for and build extra bulkheads (what’s with the hate-on for bulk heads anyhow?) concealing new duct runs keeps their mouth shut and the municipality’s all over the map depending on the mood of the plans examiner or the building inspector.
Judging from the evidence we’ve gathered in the field, municipalities have no clear, even-handed approach for resolving the need for ventilation when it comes to renovations. Sometimes building inspectors bully home owners into installing Heat Recovery Ventilators (HRV) even when the OBC ventilation requirements are met by more than one exhaust fan that constitutes a principal exhaust fan and even when the house is very prone to air leakage (well over 7ACH50).
Compared to Europe and the USA, few buildings are tested for air leakage. Consequently, few professionals are fluent in air leakage metrics and the impact that air leakage has on a building’s “natural” infiltration rate. Some assume that leaks provide enough good ventilation, but ultimately they’re only guessing. So to help guide the renovation sector, this is what we have to say:
- Century-old, leaky buildings that are excessively air leaky only benefit by having ventilation systems if the home is air tight. Air seal your house then install a balance ventilation system with dedicated ducting so you can “dose” the fresh air per occupant designed per CAN/CSA-F326-M91.
- A good ventilation system is balanced (out with the bad, in with the good), is fully ducted and earns its keep when installed in an air tight home (less than 2.0ACH50).
- If municipalities compel home owners to add more mechanical ventilation, they should justify it with results of an air tightness test and also recommend the house be made more air tight. Don’t rely on the HVAC technician to cobble something on the spot.
- Discourage fireplaces and seal up Rumfords, install sealed combustion appliances, promote the sexiness of induction cooktops and electric broilers and ovens.
In 2017, Part 12 of the OBC will change to require greater home energy efficiency and all prescriptive packages in SB-12 will require balanced ventilation systems. These changes will make new homes perform that much better, again, than vintage homes. However it would be unfortunate to see the municipalities push for balanced ventilation systems in partial renovations as a knee-jerk reaction without requiring that the building also be more air tight.