One of the big challenges of making a house warmer with insulation and/or draught proofing (both of which make a house more airtight) is that by reducing draughts we have the potential to trap moisture, particulate matter and chemicals in the house, and actually cause problems to the house and/or our health. Before we go any further let’s begin by saying that we are not advocating over-warm houses – there is lots to be said for living on the cool side. Secondly we are not saying don’t do anything other than putting an extra jumper on. What we want is comfortable, healthy houses with affordable bills.
Houses breathe in three ways:
- Through deliberate gaps where air can flow, eg an open window, where we can choose to close it
- Through unintended gaps around pipes as the enter or leave a building, and gaps left in the building process
- Buildings also breathe through their surfaces – moisture particularly moves through older walls
The benefits of draughts and walls breathing in a house:
- The air is continually changing in the house, stale air is replaced keeping air quality is high and moisture being produced in the house should escape naturally
- The walls themselves may absorb and return both and moisture and warmth to the house
The negatives of draughts in a house:
- The house will cool down quicker than for an equivalent, less draughty building
- The cost of heating and maintaining a given temperature will be higher than for an equivalent, less draughty building
- Draughts cause people to feel colder
- If the house or some rooms are under-heated moisture may build up on and in colder walls
The benefits of adequate, controlled ventilation:
- Air quality is improved and humidity is reduced
- Heat loss is reduced and therefore heating costs are lower
- The fabric of the building is protected
- Heath of occupants is better
The negatives of houses with inadequate ventilation:
- Possibly poor air quality – this includes particulate matter in the air and chemicals being released from the fabric and contents of the house
- Moisture from washing, cooking and living can condense on cooler surfaces and cause damp and mould. Moisture can get into the walls and become trapped within the walls
- Occupants’ health can be impacted
- Dampness in insulation can reduce its effectiveness
- Timber and other materials can be damaged by the damp
Monitoring
Relatively cheap moisture meters are available, designed to test walls and timbers for moisture content. You can buy meters which read the humidity of the air in a room. Checking the air quality is a more expensive challenge.
Draught proofing
Sealing gaps in the fabric of the house will reduce draughts, flexible fillers are great for holes and spaces around pipes or in the fabric and brushes and draught stripes are ideal for sealing doors and windows which need to be opened and shut.
Insulation
Synthetic insulation is often (but not always) non-breathable, whilst many natural materials are used to create more breathable insulation products. Care is required if additional insulation is being added to avoid creating problems with damp in the future.
- Internal wall insulation:
- Moisture impervious insulation needs to be installed with an air space behind it, ensuring that the wall can still breathe – the air and moisture in the room needs a way to be removed .
- Breathable insulation can be attached directly to the wall and will allow the wall the breathe as designed. Care is needed that the plaster and paint also encourage breathability
- Loft insulation – if the ceiling is insulated care must be taken to ensure there is still ventilation in the loft
- Suspended floor insulation – ensuring the void below is dry and has good air flow is essential There should be air bricks, which should be checked to ensure they are not blocked or covered.
Ventilation
- Windows are now built with trickle vents, which allow air flow
- Doors – internal doors usually have a space below to allow air to circulate in a house. Under door draught excluders will reduce this though monitoring moisture levels in rooms and checking cold surfaces for damp is a wise precaution if you are reducing airflow, especially if your rooms are not all equally warm.
- Extractor fans in bathrooms and kitchens can help remove moisture and by pushing air out of a house can also encourage fresh air to be drawn in, improving indoor air quality. Many houses now have low power extractor fans designed to run continuously.
- Mechanical heat recovery – a ventilation system which recovers some of the heat from the air being expelled and pre-warms the replacement air. Available as a whole house system or for a single room and easily retrofitted using the hole from a pre-existing extraction fan
- Smart ventilation – can monitor air in a room or below a suspended floor. The vents can open or close automatically as needed. Available as passive systems or powered providing mechanical ventilation if required. By closing the vents when air quality is good, heat loss is reduced.