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Maintain Good Ventilation Without Losing Heat

Older homes are often characterised by draughtiness, with fireplaces open to the chimney and draughts around windows that allow cold air in.  The Building Regulations have addressed this over the years and modern homes are designed to be more tightly sealed, reducing the air flow into and out of the building, except when intended by opening windows.  This is great for reducing heat losses and keeps our energy bills down.  However, it can mean poor air quality and condensation problems, which can lead to unsightly mould growths and affect health, e.g. asthma and allergies.  Windows and trickle vents can help but another solution is mechanical ventilation with heat recovery.

This was an issue in our house, which was built in the 1970's.  In the winter months we turned the thermostat down and the heating was not on whilst we were at work nor overnight so as not to waste gas.  However, we found that we got a lot of condensation on and around the windows in winter.  The problem can be resolved by opening the windows and regularly airing the house but the resultant loss of heat made our central heating system work harder, increasing energy consumption. 

Also, our house was fairly draught-proof as the double glazing had been replaced in the 1990’s, including the back door and patio doors; the front door opened into a small hall with a door to the living area.  Therefore, our solution was to install a Genvex Mechanical Ventilation with Heat Recovery (MVHR) system supplied by Total Home Environment.  This removes stale, damp air and expels it to outside, first recovering the heat from it.  This heat is then used to warm up the replacement fresh air, which is then distributed to the living areas.  This gives a warmer home with good air quality, no condensation problems and lower fuel bills.

The unit was installed in April 2008 at a time when there was no other work going on at our house.  This is an issue for the supplier company, who mostly work in the new build or renovation market, where there is usually an electrician on hand as well as a builder to help lift the unit into the loft and so they only need one fitter.  We had to find someone to do the electrics, help lift the unit into the loft and make the holes in the outside wall for the ducts – our local electrician was able to help and I got involved in the lifting.

The manual we were provided with was written in English translated from Danish and was not easy to follow, hopefully by now it has been rewritten.  We persevered with it, but could see that would be difficult for someone less committed to the system. 

We are happy with the performance of our Genvex MVHR; it has solved our condensation problems during the winter, which is a major improvement as far as we are concerned.  We are also pleased with it in terms of air quality and find it does not take a lot of energy to run.  We have now been able to redecorate around the windows to get rid of the old mould and condensation marks.

In terms of heat recovery it is also performing well:

• Outside air temperature - 4.3ºC
• Inside room temperature in Music Room - 18.1ºC
• Temperature of air extracted from kitchen & bathroom - 19.9ºC
• Temperature of air supplied to living areas - 13.9ºC
• Temperature of air exhausted to outside - 7.2ºC

What this means is that much of the heat in the air extracted from the kitchen and bathroom is actually retained by heating up the incoming air that is supplied to living areas.  The air expelled to the outside is not much warmer than the outside air.