What is a hybrid system?
Conventional heating and cooling systems relying on electric or gas boilers or furnaces and electric air conditioners have been the norm in the US for years. This situation is changing as energy prices increase and climate change becomes an issue we must all address. As we try to include ‘green’ and/or cheaper energy sources into our homes and businesses, hybrid systems which rely on more than one energy source have become quite common. The main reason for this is that providing all the energy required to heat or cool a house from an ‘alternative’ source can often be difficult or expensive.

Conventional systems have also relied in the past on one distribution method, usually forced air, baseboard or radiant floor. We are now seeing more and more multiple distribution systems. These can also be regarded as hybrid systems and are usually designed to accommodate more than one source of heat or to improve comfort. You might have radiant heating powered by solar thermal as much as possible but rely on forced air for back-up heating and cooling. You might also want mild radiant floor heating for comfort but again rely on ducts for primary heating and cooling and for indoor air quality.

Why would I want a hybrid system?
You may want to install solar thermal panels for your heating requirements but providing 100% of space heating from solar panels is very difficult unless you get acres of panels coupled with a huge storage tank or have an incredibly well insulated house. The answer to this problem may be to use solar heat when possible but combine it with a gas boiler for those particularly cold and/or cloudy days.

Maybe you recognize the merits of geothermal heating and cooling but find a full system which will heat your house in all weathers beyond your budget. You could install a ‘split’ or hybrid system which would provide all your AC and most of your heating but revert to gas heating in particularly cold spells. This could save you a lot of capital cost on the system and still use geothermal for 80% of your heating.

Have you fallen in love with warm floors provided by radiant heating but find that you cannot provide all your heating through your beautiful wooden floors? Or maybe you want the warm floors but also want forced air to provide filtered, fresh air in the winter and cooling in the summer. A hybrid system is again called for with all its complexities.

These are only a sample of the reasons that many people are installing hybrid systems these days but, no matter the reason, the design of the system is rarely easy.

What are the problems with designing and running a hybrid system?
Control is by far the biggest problem to overcome when installing almost any hybrid system. We strongly advise you to use the services of a professional who is familiar with hybrid systems to ensure no mistakes are made in your system. There is a clear danger in using a specialist contractor to install one part of your system with its own control system with no thought to the overall system.
If you are using two energy sources such as solar thermal and a gas boiler the problem is to maintain the necessary temperature in the radiant system to supply the needed heat and to ensure that the solar is used as much as possible.
If you are using solar thermal to power a radiant floor and a gas furnace to provide back-up through a duct system the problem is to ensure that the radiant floor is used as much as possible and that the gas furnace turns off when not needed.