Breathe Easy…
Clarissa Youden, of Total Home Environment Ltd, discusses the various forms of ventilation available on the market and how Heat Recovery Ventilation can offer the most dramatic health benefits and substantial fuel savings
insulated and sealed-up to save energy, that they can barely breathe. Think of all the VOC’s (Volatile Organic Compounds) that naturally occur in your home, leaching out of soft furnish- ings, chipboard, paint, plastics, scented room sprays… and what if you’re in a Radon Gas area? You spend 70 per cent of your time at home and you breathe over 10,000 litres of air a day – don’t you want the cleanest, healthiest air in your home for you and your family? In perspective, to live in comfortable condi-
V
tions, an adult needs approximately 30m³/hr of fresh air. In a typical bedroom of say 36m³ with two adults sleeping in that room, you’ve got less than an hour before CO2 and water vapour will build up with condensation and mould spores forming… not great for Asthma and allergy sufferers. Why are we then ‘ventilating’ the property by
poking holes through the skin everywhere with archaic technology – draughty unfiltered trickle- vents in window frames (that people then shut because they’re too cold) and noisy extractor fans in kitchens and bathrooms (which are never cleaned, so block-up). In both instances we’re just throwing away vital heat. This ventilation contributes between 50-60 per cent of the typi- cal heat-loss of a home – half your heating bill goes to mitigating the effects of ventilation.
entilation in homes is essential. As Building Regulations tighten-up, so do homes; homes are now being so well
If you’re in a town, do you want to let the pollution in? Besides, most people are out in the day and then don’t want to open windows at night.
Passive Stack Systems
These systems work via natural air movement, motivated by a temperature difference between the inside and outside of the house. Pipework goes from ceiling vents in wet rooms up through the roof, but you still have to have some background ventilation in the form of trickle vents and extractor fans, meaning more cold unfil- tered air. Also, it tends to work best, in the colder months of the year, when you have the bigger temperature difference, so it can get a bit stuffy in warmer weather.
Positive Input Ventilation (PIV)
A fan unit brings fresh filtered air from outside into common areas and forces stale air out of the building via natural leakage in homes which are not so airtight. Although it can be set up to take air from a cold roof as well, (warmer air than outside) mostly air will be introduced at whatever the temperature is outside, plus you are still throwing heat away with this system.
Mechanical Extract Ventilation (MEV)
Economical and easy to install, especially in a retrofit installation. A fan unit located remotely extracts air out of wet rooms through ductwork. Designed to work at a low level with an occa- sional boost when required, it again needs the dreaded heat removing trickle vents. Research has also suggested that MEV doesn’t give enough clean air (CO2 was found to be above the recommended maximum of 1,000 parts
So, how do we guarantee good indoor air quality but not lose any heat? We know trickle vents or extractor fans won’t cut the mustard, but what about other types of ventilation?
Controlled Natural Ventilation
AKA ‘opening windows’! To meet the 0.44 air changes per hour, set by Building Regulations in England, you’d need to open all the windows for 10 minutes, seven times throughout the day!
34 selfbuilder & homemaker
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Even with the best HRV systems, there is still heat available to recycle. If your home is really well insulated and airtight, you could take advan- tage of a premium ventilation unit which integrates a micro heat pump within the HRV unit to harness far more energy from the outgoing
Good HRV systems will be PassivHaus certified, have an automatic summer bypass (no heat recovery in hot months), trap pollen and aller- gens down to 0.01 microns and save about a third on your heating bills.
per million). Phew – ‘Is there any answer to my problems?’ I hear you say. By George, yes there is.
Heat Recovery Ventilation (HRV/MVHR)
This is whole house ventilation at its best, completely controlled to provide the correct amount of fresh air, when it’s needed and with great heat recovery. A fan unit located remotely continuously extracts stale air out of wet rooms while drawing fresh filtered air from outside. They pass each other in a heat exchanger (not mixing) and up to 96 per cent of the heat from the stale air is transferred to the fresh air being put into the habitable rooms of the home.
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