HVAC sizing is a design decision about the home's heating and cooling needs. It is not simply a choice between small, medium and large equipment. When collecting installation proposals in Ottawa, ask each provider to explain how the recommended capacity was selected and what information about your house supports it.
Ask for the basis of the recommendation ENERGY STAR recommends verifying system size with a home-specific calculation such as Manual J. The purpose is to evaluate heating and cooling requirements rather than rely only on the size of the old equipment or a square-footage shortcut.
You do not need to perform the calculation yourself. Ask what was assessed, whether the calculation reflects the current home, and whether the installer can explain the result in ordinary language. Keep a copy of any summary provided with the proposal.
Tell the installer what has changed List additions, converted spaces, window work, insulation improvements and rooms whose use has changed. Tell the provider about persistent comfort concerns. A house that has changed since its existing system was installed deserves an assessment that reflects those changes.
Separate the area you want conditioned from storage or other spaces with different requirements. Ask the installer how those spaces were treated in the design rather than assuming every square foot has the same demand.
Distinguish equipment capacity from room comfort The total system capacity is only one part of the project. Ask how air will be delivered to the rooms and what work, if any, is proposed for distribution. If a room is uncomfortable, have that concern documented alongside the equipment selection.
For example, a homeowner might request a larger unit because an upstairs office stays warm. The proposal should explain the cause of that room's problem and how the recommended work addresses it. A larger number on an equipment specification is not that explanation.
Compare proposals using the same home information If two companies recommend different capacities, ask both to identify the assumptions behind their choices. Were they considering the same conditioned spaces, planned improvements and equipment configuration? Did both assess the distribution system?
Do not choose by averaging the two recommendations. A disagreement is a reason to ask for the supporting assessment. Keep model numbers and design summaries together so you can compare the complete recommendations rather than isolated capacity figures.
Ask what happens after sizing Equipment selection, installation and startup are related steps. Ask which indoor and outdoor components are matched, which controls are required and what checks will be recorded when installation is complete. Clarify whether changes to the home before installation would require the design to be revisited.
If a renovation is planned, discuss it before signing. The goal is a system suited to the intended home, with the sequence of work clearly understood.
Can I size equipment from an online calculator? A simple calculator may help explain concepts, but it cannot replace an appropriate on-site assessment and professional design.
Should I automatically keep the same capacity? Ask why that capacity remains appropriate. The old label is useful information, not proof that the new system should match it.
Is bigger a safer choice? Not automatically. Appropriate capacity and a complete design matter more than choosing the largest option.
Use the replacement checklist to record changes to your home and the rooms that concern you. Those notes give each installer the same starting point for a more useful proposal.