Simultaneous heating and cooling with heat pumps
We’ve all seen the heat requirements of new building come tumbling down thanks to building regulations, planning legislation and a general drive to save carbon emissions. It still surprises me that buildings in the 1970’s had heat losses as high as 188 watts per square metre; we are now in the 40s. As our standard of living expectations have grown, some buildings now even need more energy for hot water production than they do for heat.
The reduction in heating loads are a result of greater levels of insulation and air tightness. But this level of air tightness has an unintended consequence:the need for cooling in summer. Imagine the thermal gain of a contemporary designed new home or office block with lots of glazing and limited shading.
With my heat pump hat on, heat pumps make an ideal solution in this scenario. Heat pumps are reversible and can be used to both heat and cool a building. And as they use environmental energy to perform this process, heat pumps are a much more efficient way to cool than using standard air conditioning units as they can cool both passively and actively. A ground source heat pump can extract heat from a building and put it into the ground; meaning that it can passively cool whilst only expending the amount of energy required to drive a circulating pump. Only if the building requires more cooling does it need to start its compressor and cool actively.
Even more than this, I have noticed a growing trend of buildings in the last 3-4 years requiring heating and cooling simultaneously. And guess what? Ground source heat pumps can in fact not only do both; they can do both at once, with emitters drawing from the hot or cold side of the heat pump as required. If we return again to our example of the heavily glazed contemporary building, the sunny, south facing side with a large glazed wall onto the garden may need cooling whilst at the same time the north facing snug, with only a small amount of glazing, needs heating. This, of course, is also an issue for larger buildings with different zones having widely different usages.
The first step to delivery of simultaneous heating and cooling is to consider your emitters and the cooling load required. Underfloor heating systems can be used to chill a building, but only to a certain point; below the dew point they will cause condensation to form on the floor. Fan coil radiators (whether wall or ceiling mounted) are ideal because they contain condensate drains and can deliver more energy without causing condensation issues.
A recent example of this in action is a project we’ve just completed for a major new build transport hub. This system incorporates a ground source heat pump and fan coils and has the ability to heat and cool individual zones simultaneously as they require. Waiting areas often need heating because of doors being continually opened and closed, whereas office areas in the same building, with their lower infiltration rates and high load of IT equipment need cooling.
One thing to note is that we only recommend this approach for borehole systems and that due care needs to be taken to ensure that your boreholes can sustainably accept the amount of heat you need to sink.
So if you think you might have a project where this kind of innovative approach might be helpful, don’t hesitate to give us a call today.