HVAC System Design Ottawa

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HVAC System Design


HVAC System Design Ottawa

What new homebuyers need to know about HVAC System Design and compliance with building codes.

The National Building Code of Canada is one of the most impressive documents ever compiled in our country. The documents is an input from engineers, architects, utilities and builders. While it is widely used and regularly updated by professionals to comply with today’s building designs.

The most recent addition of the Supplementary Standard SB-12 to the Ontario Building code moved it beyond constructing safe buildings. It was the addition of energy efficiency to the Ontario Building code, which was practically ignored in previous updated editions.

The HVAC System Design consists of two discrete components: one, is the heating and/or cooling device itself, two is its performance with respect to its design.


Once municipalities, specially Ontario, began demanding heating permits, contractor heating plans had to be approved in advance. Systems than were inspected, however the poor performance of many two-story, brick veneer tract housing heating systems is scandalous.


Air Conditioning, Heating and Refrigeration Institute “AHRI” develops industry-recognized performance standards for industry equipment. To register any HVAC warranty with the manufacturer’s, the system must consist of AHRI rated components.  The evaporator coil must be AHRI rated for use with the outdoor units. If the AHRI certificate approves a particular combination of indoor and outdoor unit to achieve 16 SEER “Seasonal Energy Efficiency Rating” at 1000 cfm, then the duct system must be capable of moving the rated airflow.

So many new homebuyers find out after the initial first year, when their heating system is maintained by a HVAC contractor, the airflow is drastically changed. For example, the master bedroom which did not have a good airflow, suddenly felt nice and warm after the maintenance was done. Why wasn’t that efficiency caught at start-up?

Well, it is simply due to improper practices by the builders. Often, the newly fired gas furnace would be used as a heater for the construction site causing tremendous damage. Ideally, air handler operation must be avoided until “carpet stage”. Builders should use alternative heating methods for the construction site such as natural gas radiant heat. It is highly recommended that new homebuyers consider doing a furnace maintenance and cleaning once they move into their new home. Although it may seem unnecessary as the system has barely been used by yourself. However it may save you much on energy consumption once assured the system is running at its peak of performance as AHRI rating states.


Once the heating and cooling systems have been installed, we must verify that the expected performance of equipment actually exists. The system start-up or commissioning should follow several tiers.

Tier One Commissioning: Once the building is under reasonably clean conditions, each outlet should be tested with a properly calibrated air hood or air flow meter. This will verify the specified volume of air is flowing to each outlet. Any problems with poor airflow, either supply or return will show at this stage.

Tier Two Commissioning: When the building reaches “carpet stage”, and is clean enough to start up the furnace without damaging construction. At Tier Two a secondary airflow check should be commissioned with all the grilles and registers installed. Depending on each season, there should be start up documentation showing the performance data. All Tier Two commissioning documents should readily be available to service technicians on future maintenance or service calls.

Tier Three Commissioning: Tier Three Commissioning is really part of Tier Two as each newly installed unit must be checked during its season for use. For example an air conditioner should be tested when the minimum outdoor temperature reaches 65F along with an indoor temperature between 70F and 80F. Same goes with the newly installed furnace. The furnace should be tested during fall or beginning of winter, when the outdoor temperatures are reasonably cooler.

We must verify the expected performance of equipment and systems actually exists at every Tier Commissioning. Sometimes contractors cannot afford to include the pricing of commissioning cost into their bids, which will make them uncompetitive. Typically the end user, which is the new homeowner ends up paying on furnace or air conditioner service calls.


Therefore, when we spoke about the HVAC system design consisting of two major components. One being the systems and the other being the performance expected. However since many HVAC Contractors do not perform multi tier commissioning when installing new residential heating and cooling units, many underperformance problems arise. Therefore the expected performance rating by AHRI will not be met. Until the time that residential commissioning is added to the building code every new home buyer should consider a cost to have a maintenance done on their systems as soon as they move into their homes.

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