Unit Heaters 101 - An Intro to Garage, Workshop, and Greenhouse Heating
Everything You Need to Know to Get You Started With Heating Non-living Spaces, Such as Your Garage, Workshop, or Greenhouse
So, you’re thinking about installing or replacing a heating unit in your garage, workshop, greenhouse, or another non-living space. With this guide, we hope to help you better understand the options available to you, as well as answer questions as to why one may be better than another for your heated space!
What are the main heating systems for garages, workshops, or greenhouses?
This isn’t a straightforward answer; for residential garages with day-to-day car parking and light use, power vented unit heaters are the most popular across Canada. For spaces with in-floor heating installed, a boiler system is often used. For larger workshops, warehouses, or greenhouses, you will find a mixture of unit heaters, boiler systems, radiant heaters, and even furnaces being used!
What types of energy or fuel do garage, workshop, or greenhouse heaters use?
Across Canada, the most typical energy source for garage heaters is either Natural Gas (NG) or Liquid Propane (LP). We are starting to see the emergence of electric (EL) unit heaters, although these do still have significantly higher operating costs compared to a NG or LP combustion heater. We will update this guide as we see the emergence of more environmentally and operating-cost friendly electric heating solutions.
What is a Unit Heater or Space Heater?
Unit heaters, also commonly referred to as space heaters (although they are only a type of space heating), are a type of heater that is used to heat non-living spaces, such as garages, workshops, or greenhouses.
What types of unit heaters are there?
There are a number of different residential unit heater types, with each being a better fit for different environments. The main types in use across Canada and their typical usage environments include:
- Power Vented NG/LP Heaters: the most common, standard air flow unit heater for use in residential garages, workshops, or greenhouses; you will find power vented unit heaters most often suspended from the ceiling or placed high on a wall
- Separated Combustion NG/LP Heaters: garages or workshops where the air is polluted or contaminated with possibly combustible fumes or fine, airborne particles like in a carpenters workshop. Like power vented unit heaters, you will most often find these hung from the ceiling or mounted on a wall, saving precious floor space
- Radiant Tube (NG/LP) Heaters: great for non-cluttered spaces where heating is maintained at a constant temperature and the exposed surfaces are not cluttered (such as garages, warehouses, or storage units). Radiant tube heaters are almost always ceiling mounted, give them a clear line of sight to the targeted heating areas
- Residential Mid- or High-efficiency Forced Air Furnaces: yes, a furnace can be used in your garage or shop! These are more complicated and involved to install, require ducting, and often tend to take up precious floor space as compared to the other options listed above. However, some furnace models can be installed horizontally, allowing them to be suspended - make sure to double check this before installing sideways!
I only use my heater sometimes - what type of unit heater should I buy?
If you plan to only intermittently use your unit heater, you are probably best off installing a power vented or separated combustion (air flow) heater. The reason for this is that these heaters only heat the air, rapidly increasing the temperature you feel in the heated area. Radiant heaters heat the surfaces exposed to the heater, so this is a much slower and thorough heating process. In summary, for intermittent usage you will use much less energy to heat the air in a space to a comfortable temperature than it does to heat all the surrounding surfaces and furnishings.
I want to maintain a constant temperature in my garage/workshop/greenhouse - what type of space heater should I buy?
If this is you, any of the listed heaters will work. However, we do recommend considering a radiant tube heater if you have an uncluttered space where the floors and walls are exposed. We have found that radiant heating is most efficient when maintaining a stable temperature, heating surfaces so they are warm to the touch. As a bonus, floors and walls tend to dry much more quickly with a radiant tube heater as these surfaces are warmed directly. This will help to reduce the buildup of puddles on garage and workshop floors.
How efficient are gas unit heaters?
Most power vented and separated combustion unit heaters have efficiencies in the range of 80%-82%. Modern forced air gas furnaces will range from 90% to 97% efficient, depending on the model and build, but these do come with more upfront installation costs and will require drains for the water condensate. Radiant tube heaters will usually have efficiencies higher than a forced air unit heater, but that does vary depending on the configuration and layout of the room, material of the exposed surfaces, and floor/wall clutter. Condensing boilers, for in-floor heating systems, typically have efficiency ratings around 95%.
How do I control my garage, workshop, or greenhouse heater?
Fair question, especially when these heaters are often mounted well out of hands reach high on a wall or suspended from the ceiling! The short answer is, the same way you control the heating in your home - with a standard thermostat.
Most thermostats will work just fine for these application areas, but, if you are working on a budget, we do typically recommend you install a simple, non-programmable heat-only thermostat. The reason for this is that your heater is exactly that - a heater, no air conditioning is possible. Also, you typically won't require all the bells and whistles that fully programmable controllers offer when installing them with your unit or space heater. The choice is yours!
How are unit or space heaters sized?
Gas (NG or LP) heaters are sized based on the combustion heat created, rated in BTUs. Most residential applications require between 25,000 BTUs to roughly 120,000 BTUs. This means most residential applications will typically only require a single unit heater to properly heat their garage or workshop space.
What size of heater do I require?
This depends on many different factors, from the build materials, insulation levels, and even your geographic location - you need more heating for the same building in a -35°C environment as compared to a 0°C environment.
We are working on a detailed answer to this question, and will update this guide when that is ready to share! In the meantime, if you aren't sure, reach out to our team here for more support.
Special safety note about using a forced air furnaces for workshop or garage heating applications:
In Canada, it is not allowed to use a furnace for both a living space and a non-living space (such as a garage or workshop). This is due to the risk that motor vehicle or similar exhaust fumes are circulated into an occupied living space, creating a dangerous situation for anyone inside.
Consider the scenario where you have a finished loft or office space above your garage – you need to consider that you will need a separated forced air heating systems if that loft or office space is considered a living space.
Tips for when using a radiant heating system:
- Don’t use rubber mats or other insulating coverings on your floor - these will prevent the radiant heater from thoroughly heating the ground, resulting in much lowered heat retention and causing your heater to work extra hard
- Try to limit the amount of hanging wall coverings, like posters or fabrics
- Reduce the floor clutter as much as you can for optimal surface heating
Jim Filteau said:
Thank you for all of the thorough, detailed information.