Heat Recovery Ventilation

Heat Recovery Ventilation

Heat-RecoveryHeat Recovery ventilation is a mechanical form of ventilation with the added advantage of collecting heat directly from the warm moist areas of your home such as the kitchen or the bathroom and using it to heat the incoming air so that no cold air enters your dwelling (often shortened as HRV or MVHR). The MVHR is normally situated in the attic area.

A MVHR system has the capability of providing sufficient fresh air at all times to your home. On extremely cold days when the air out side is very still the mechanical ventilation ensures more than adequate air changes inside your home.

In Passive homes MVHR system are mandatory where no passive ventilation units exist. MVHR systems are of little value in an air leaky dwelling.

People breathe by taking in air, using the oxygen and exhaling the waste. Buildings need to operate in a similar fashion, in order that they remain fresh and habitable. A certain amount of air needs to be continually taken in, and an equivalent amount exhausted to outside. The problem with this is that outside air is usually at the wrong temperature for consumption, and can prove costly to heat. An increasingly popular solution to this problem is to use the heat of the air being exhausted to warm the air being drawn in. As this is a process whereby heat is being recovered from the outgoing air, it is termed Heat Recovery Ventilation (HRV).

HRVIt works by enabling the two air streams (in and out) to move through one another without actually mixing. In this way, one air stream warms the other. This is done inside a counter- flow heat exchanger, which is made up of hundreds of individual air channels. A tiny section of the internal workings of the heat exchanger is shown above in Figure 1. This ingenious design is such that each incoming fresh

air channel is surrounded by three outgoing exhaust air channels and vice versa. The exchanger is a cleverly arranged collection of polystyrene sheets welded together and installed within a casing called an Air Handling Unit (AHU). This AHU also contains fans to drive the air in and out, and filters to clean it. The ProAir series of AHUs have been specially designed, for this technology and can be sized to suit any residence, from the one bedroom apartment to your villa in the hills.

energyEfficientHomeIn these days of global warming and serious environmental issues we are urged to conserve energy in all aspects of our lives. We can contribute, by making our homes as energy efficient as possible by ensuring that insulation and air- tightness levels are as high as possible, and heat loss is minimised. This can only achieve so much because, as a practical unit, a house and its occupants will need to breathe, as we can’t live in a sealed box. Without some ventilation, the many water sources within a home will cause condensation and the air people breathe can become stale and carbon dioxide laden.

The answer to this is to have the air in your house regularly changed in a controlled, energy efficient manner, using a heat recovery ventilation system.

So, if you are planning to go green and either build new or renovate/refurbish, you should first think of investing in the building envelope and everything else will look after itself. What is meant by this is that, if you adopt a strategy of (a) high levels of insulation, (b) extra care in draft- proofing and (c) HRV, then a much reduced heating system will be required. This will result in not just a lower initial capital outlay, but will keep those irritating utility bills at bay, no matter how high the price of a barrel of oil.

 

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