Your garage remodel should include an HVAC system that will provide outstanding climate control while keeping your energy costs as low as possible.

Your Existing System Shouldn’t Be Enough

Garage HVAC Ventilation

Time to upgrade the garage ventilation

Have an HVAC contractor take a look at your current system. If he or she tells you it is adequate to also serve your converted garage, then something is wrong. In most cases, you will not be able to heat and cool an additional 450 to 650 square feet with your current system.
The first possibility is that the HVAC system was sized to be too large in the first place. If so, you’ve probably been paying too much for heating and air conditioning, because the efficiency of systems that are too large suffers significantly.

The second option is that the technician hasn’t done an accurate assessment of your needs. In either case, ask the HVAC pro to show you the math to back up the claim. A full load calculation might be in order.

We’re not trying to talk you into buying a second system when the existing system has enough capacity to take on the additional square footage. What we’re trying to avoid is you having a single HVAC system that no longer adequately heats and cools either the existing home or the remodeled garage.

Getting multiple estimates from HVAC contractors always makes sense when determining the right size as well as the cost.

Installing a Single New HVAC System

If your current system is more than 15 years old, replacing it with a new system large enough for the existing space plus the remodeled garage is the most cost-effective choice. You’ll increase efficiency by 25 to 50 percent if you install a heat pump and up to 20 percent if you replace a furnace with a furnace.

These savings are possible because new heat pumps and central air conditioners offer SEER ratings of 20+. Heat pumps deliver HSPF heating ratings of 13 and higher. Just 15 years ago, top units offered about 14 SEER and 8 HSPF. The most efficient furnaces from Lennox, Trane, Carrier and other top brands deliver AFUE efficiency of 97 percent or higher.

For HVAC systems 10 to 15 years old, have a trusted HVAC pro give you an opinion on how long the system should last without major mechanical problems. It’s not an exact science, of course. You might decide to replace it; you might hang onto it when you factor in age, efficiency and costs for new equipment.

An HVAC System Dedicated to the Remodeled Garage

If you do not plan to replace your existing HVAC system, a mini-split ductless system is the ideal choice for a garage conversion. The system uses a heat pump that heats in the winter and provides air conditioning in the summer.

The condensing unit of a mini-split system is installed outside. Indoor units are installed in one to four places. Refrigerant lines and drain lines connect the outside and indoor units, and just small holes in the construction are required. The indoor units have fans that circulate the hot or cold air being produced.

This method of installation eliminates the need for ductwork and the expense it represents. Ductless heat pumps can be very efficient, and they’re very quiet too.


Take your time evaluating the HVAC system because climate control and energy efficiency are important factors in a garage conversion project. Talk with several reliable HVAC companies to get accurate information and written estimates to compare for the proposed work. Doing your due diligence will pay off in comfortable living space and reasonable energy costs.

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