Modern built homes are getting more energy efficient due to the use of insulation and breathable membranes houses are know being tested for air permeability. This drive to energy efficiency creates a major problem in that in the summer months even in the UK the buildings overheat which naturally is not conducive to a pleasant environment particularly during the night when we need sleep.

Good ventilation is a requirement and is easily achieved using a mechanical ventilation system but this though extremely efficient at filtering and removing the used air will not cool the house due to it being determined by the incoming temperature of the outside air temperature. In the summer months this temperature particular at night can be unbearable so what can we do to try and keep the temperatures to a reasonable level and condition the air.

Electrically driven air conditioning units are a option but they come with some major disadvantages, firstly they are expensive to operate and this overuse of electric is compounding the global warming issue and they need maintaining. Secondly they do not remove the used air but instead just recirculate it so any contaminants are not removed from the building.

The best option is to take advantage of what the earth provides for us for free and in this case it is through the use of passive cooling via the utilisation of earth pipes referred to as Ground Air heat exchangers so how do they work?

In the UK we are blessed with lots of rain and average temperatures which means that the grounds temperature 1.5 to 2 metres below ground remains at a fairly constant temperature of 7 – 12°C so the solution is to draw the fresh air to supply the ventilation unit through the earth and deliver the supplied air into the building within this temperature range and thereby cooling the incoming fresh air by as much as 13°C approximately depending on ground conditions in the summer with the added benefit of warming the incoming air in the wintertime by 10°C.

It is important to not here that the ground conditions play a major role in the effectiveness of this system the ideal being damp soil surrounding the ground pipes will perform rather better than free draining soil. Design considerations are important when using this type of system to achieve the maximum benefit for achieving these changes in temperature. The ground pipes need to be sized accordingly but generally speaking for a large property 60 metres of ground pipe with a diameter of 200mm would be required, this can be laid out in a pattern to optimise the soil conditions, Rehau make a excellent system.

Another design consideration when using ground to air heat exchangers is using the right pipe for this purpose, antimicrobial polypropylene helps protect again bacteria and microorganisms equally the ground pipe system needs to have significant fall to prevent standing water and this needs to be drained away via a condensate trap.

Another added option to further enhance the cooling effects in the summer months would be to include a cooling unit such as the Comfocool manufactured by Zehnder, this unit is designed to work with ComfoAir Q 600 heat recovery ventilation unit. The comfocool sits on top and provides a further 1.5 Kw of additional cooling if further enhancements are required.