Dampness often occurs within older properties, which can result in black mould growth, fungus infestation and also increased house dust mite proliferation.
Dampness can be caused by a number of reasons:
- Faults in the building fabric, e.g. leak in the roof or in flashings, cracked pointing of stone walls or blocked gutters, etc.
- Rising dampness from the foundations
- Cold spots on external walls or generally poor insulation (cold bridges)
- Poorly performing windows (cold surfaces)
- Leaks in the plumbing, drainage or heating system
- No proper extract ventilation system for wet rooms and the kitchen
- Too little ventilation generally
Especially after older properties have been renovated and upgraded, it is a fairly common issue that dampness problems starts to appear. Dr. Sterling Howieson of Strathclyde University stated the black mould risk triples in such cases. Reason for this is the increased air tightness through insulation and new windows, in conjunction with unavoidable cold bridging in such properties. Therefore when buildings are being renovated, it is vital to incorporate an adequate ventilation strategy, in order to avoid the well-known sick-house syndrome.
Our advice for owners of buildings with dampness issues is to first check and potentially deal with all structural or plumbing issues, in order to avoid moisture getting into your building from the outside or from pipework.
If this has been checked or addressed, properly specified and installed heat recovery ventilation systems will make a difference as they not only provide sufficient supply and extract ventilation to all areas of the building, but also actively de-humidify in the colder seasons. The heat recovery and de-humidification effect is passive and therefore basically free of charge, apart from the two low-energy fans that power the system. As such the indoor humidity levels can be drastically reduced and adjusted to the desired level. Unless there are structural or plumbing issues, this will effectively deal with the most common underlying reason for mould growth.
Depending on the specifics of each building and to which extent ductwork can be installed, different types of MVHR systems can be retrofitted:
- Whole house MVHR systems with supply and extract ducting can e.g. be fitted into the loft of bungalows or two smaller storey buildings, if risers can be installed in fitted wardrobes, etc. Incorporating ductwork into the loft is often not difficult, especially when the loft insulation is being upgraded afterwards.
- Cascade MVHR systems with small extract ducts where this is possible.
- De-central MVHR units without ductwork