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An Alternative Approach to Ventilation in Newly Built Homes

"Build tight, Ventilate right"

Written by Robert Gormley, Business Development Manager 

Normally, PIV (Positive Input Ventilation) units have been used by Housing Associations and homeowners to overcome the problems of condensation dampness in both older homes, often recently modernised, as well as recently occupied newly built homes.

There is a mistaken view taken that a more energy efficient home, one that is lower in cost to heat and therefore maintains warmer temperatures for longer periods, would be free from condensation. It’s also typical for background ventilators, generally window trickle ventilators, and intermittent fans, to be installed as the means of purpose-provided ventilation to meet Part F of the Building Regulations.

However, newly built homes with low air permeability figures are just as liable to suffer from condensation problems as older, more “leaky” homes. They would therefore benefit from additional ventilation solutions and a strategy designed to account for the ventilation requirements of the entire property.

Nuaire surveyed many thousands of dwellings over many years and came to understand that residents were truly reluctant to use window trickle ventilators. Residents insisted that window ventilators produced draughts and were energy inefficient, which indeed in a modern house, they are. So, a significant part and perhaps the most important part, of this research showed that purpose-provided ventilation system was not being used by many residents. It could be fairly concluded that, according to residents, background ventilators alone are not capable of preventing condensation issues.

In understanding that PIV units have overcome condensation issues in newly built homes by providing adequate ventilation, many Housing Associations adopted Nuaire’s Drimaster PIV as their preferred method of ventilation in new build developments. The units provide freshly filtered and tempered air to the whole of the dwelling in a continuous manner. The Drimaster PIV has been shown to gently maintain relative humidity levels at rates that will prevent condensation issues and create a healthy living environment for occupants.

It has become more apparent that the provision of continuous ventilation to maintain good indoor air quality is extremely important. The government is advising that residents open windows to provide additional ventilation in order to reduce possible elevated levels of the Covid-19 virus. Opened windows require both a difference in internal / external temperature and external wind for ventilation to occur. A window opened for ventilation may indeed be called a “hit and miss” ventilator. Constantly operating mechanical ventilation units provide guaranteed ventilation and are consequently the better option. PIV units can fulfil this role; providing guaranteed, continuous ventilation throughout the home and allowing occupants to avoid any security or noise concerns that may result in keeping their windows open.

Another option again is Mechanical Ventilation with Heat Recovery (MVHR).

MVHR units provide constant input / extract ventilation, though ventilated air is distributed differently from PIV units. The extraction of air is achieved through the MVHR unit rather than through building leakage or through purpose-provided paths. Up to 95% of the heat energy in the extracted air is recovered and used to warm the fresh filtered input air. Rather than the hit and miss ventilation event of a window, the MVHR unit provides guaranteed ventilation. In using MVHR units, it is important to choose a unit that has a fully functioning mechanical summer bypass mode, which allows designed airflow rates to be maintained in bypass.

Nuaire's MRXBOX MVHR units can be matched to Nuaire manufactured Carbon Filters, either duct mounted units or the unique Q-Aire Input Carbon Filter air valve. Carbon filtration is currently used to reduce NOX gas levels, commonly associated with busy roads, to safe levels prescribed by Air Quality Reports. Nuaire has also launched a unique PIV unit, the Drimaster ECO NOX, with a Carbon Filter for the same purpose.

Nuaire Drimaster PIV and MRXBOX MVHR systems have been used in developments in which external noise, typically from busy roads or railway tracks, has had an implication for ventilation. Both systems have shown that targets for reducing noise ingress into dwellings can be achieved by their use. Both systems can eliminate the use of expensive and difficult to install Acoustic Background ventilators, particularly large window trickle ventilators. This has increased the use of both systems in New Build developments subject to external Sound Surveys.

Constantly operating energy efficient mechanical ventilation systems are still considered to be a new approach to ventilate dwellings in the UK. However, we should take time to remember that constant ventilation has always been a feature of dwellings in the UK. It was formerly provided by energy inefficient leakage paths; trickle ventilators or draughty, expensive to heat dwellings. The UK house building industry has significantly improved the construction and quality of new build homes since. SAP Assessments, combined with anecdotal evidence, shows that energy needs for heating homes has significantly reduced, perhaps further than assessments / modelling predict. This has been achieved by better insulation and considerably reducing air permeability figures.

The need to ventilate still exists. The old saying “build tight, ventilate right” is now more appropriate than ever before. Providing energy efficient, constantly operating systems is the correct approach to ventilation in UK dwellings. This coincides with current UK Government guidance to ensure that we adequately ventilate homes to contribute to a healthy indoor environment.

Nuaire can provide technical advice about the correct application of both PIV and MVHR systems in new build developments. Get in touch with one of our experts to find out more.

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