The need to ventilate
In the not so distant past open fires were the only means of heating our homes. We would heat one room, the living room, unless of course we had a fireplace in each room, but how often did we use more than one fireplace at a time. Our timber windows were draughty, our doors were draughty and our carpets would lift in the slightest breeze. As soon as the fire went out the house would quickly cool down by which time we made sure we where happily wrapped up in bed. By morning however, with no heating in the house we reluctantly got out of bed and dressed as quickly as possible. We lived in energy inefficient dwellings.
Then along came central heating systems. Suddenly we entered a new era and not satisfied with only one warm room in the house we wanted a home where all the rooms were warm and inviting. We started to use the rooms differently and we wanted more rooms so that the family could spread throughout the home doing different things. No longer were we restricted to the room with the lit fire.
So started the inevitable problem, condensation, when we reduce the ventilation rate of a dwelling and increase the overall temperature, more moisture is contained in the air, when this air touches a cool surface condensation will occur. We noticed that our single glazed windows would be covered in condensation in the mornings and that mould would start to grow.
We also soon noticed that although the house was warm, draughts started to become annoying. We wanted more comfort. So out went the single glazed timber windows and PVC double glazing was introduced.These windows, produced under factory conditions, made from a stable material, did not suffer from the problems of warping that timber windows were prone to. This meant that the rubber seals around the opening lights maintained an airtight seal so reducing draughts through the windows.
As the double glazed windows were warmer than single glazed, the condensation on the windows was greatly reduced, but not eliminated.
As always, our contentment with the reduction of draughts in the home wasn’t satisfied, so we started to seal up other openings. External doors were fitted with rubber trims, letter boxes were fitted with draught proofers and gaps between timber floorboards were filled.
When we got our homes as draught proof as possible, the cost of heating our homes increased, so we decided to insulate our homes. Loft insulation, cavity wall insulation and floor insulation were added.
Now that our homes are as airtight as possible and insulated as much as is economically possible, we find that condensation is becoming more of a problem. Surfaces that were not previously affected by condensation started to become problems areas like external walls behind cupboards, floor boards under cupboards and cold water tanks in lofts, to mention just a few, would all exhibit condensation problems.
So controllable ventilation of our home was introduced where each of the habitable rooms were given trickle ventilation, high moisture areas such as bathrooms, kitchens and utility rooms given extractor fans and lofts areas cross ventilated.
The adage “build tight ventilate right” has come into existence in the last decade or so meaning that in order to maintain an energy efficient dwelling, the dwelling should be as draught proof as possible with controllable ventilation in the right places and at the correct extraction rate.
With all this ventilation being provided is this a throwback to having a draughty home? The answer is “No” since all of the ventilation options are voluntary and controllable. We decide when to ventilate and for how long, for example when having a shower if the bathroom needs vented, when cooking if the kitchen needs vented. When we get the balance right condensation within the dwelling does not occur and we maintain the heat in our homes. When we get it wrong either we start to have problems with condensation appearing on external surfaces or we extract too much heat and have to spend more on energy.