Building a new home or a cluster of new dwellings? Do you want to make a quality home?
Historically dwellings were valued according to their size, their layout, their location and their standard of kitchen and bathroom finishes. Nowadays the value system is shifting towards recognizing the energy efficiency, renewable technologies, sustainable materials and other aspects of sustainability – and rightly so.
For new build homes we can simplify four energy efficiency standards.

Leaky Standard energy efficient dwelling
This is now the exception in new builds, which are just fulfilling the current demands of Building Standards.
Building Fabric: Standard insulated, double glazing.
Air tightness: 5-10 m3/(hr m2) @50Pa.
Heating & DHW: typically either a gas combi-boiler with radiators or a heat pump with underfloor heating.
Ventilation: Natural ventilation with intermittent extract fans, trickle vents in all windows or dMEV Systems (no trickle vents)

Standard energy efficient dwelling
This is the typical mass house builder home. Their energy standard is just fulfilling the current demands of Building Standards.
Building Fabric: Standard insulated, double glazing.
Air tightness: 3-5 m3/(hr m2) @50Pa.
Heating & DHW: typically either a gas combi-boiler with radiators or a heat pump with underfloor heating.
Ventilation: often dMEV fans (trickle vents in habitable rooms only), better: MVHR Systems (no trickle vents).

Low energy dwelling
These are homes that often they incorporate the ‘Fabric First’ approach, with better insulation and air tightness.
Building Fabric: Good insulation level with double or triple glazing.
Air tightness: 1-3 m3/(hr m2) @50Pa
Heating & DHW: various technologies are being used. We can help with far-infrared heating panels and solar assisted heat pumps for hot water.
Ventilation: MVHR (no trickle vents) or cMEV systems (trickle vents in habitable rooms).

Passive House dwelling
These homes have excellent energy efficiency levels, often in conjunction with renewable technologies.
Building Fabric: Excellent all-round insulation level with triple glazing.
Air tightness: 0-0.8 m3/(hr m2) @50Pa. For certification an air tightness of 0.6 ach@50Pa need to be achieved. A dedicated internal air tightness layer is being used.
Heating & DHW: various technologies are being used. Please note that Passive House dwellings still need a heating system. In many cases this is a downsized central heating system. In the beginning of Passivhaus their space heating was achieved with post heaters in the MVHR. In many ways this concept has proven challenging. We have successfully implemented it in many ways, but for larger dwellings we would recommend to separate the ventilation from the heating system. We can help with far-infrared heating panels and solar assisted heat pumps for hot water.
Ventilation: MVHR systems to Passive House standards (no trickle vents).
What does Building Control in Scotland recommend for new domestic buildings?
The recommendation is a staggered approach, depending on the air tightness of the building envelope:
- If the building is very airtight (0-3 m3/(h m2) @50Pa), the only choice is Heat Recovery Ventilation (MVHR)
- If is it semi-airtight (3-5 m3/(h m2) @50Pa), either MVHR or dMEV can be used
- If it is lesser airtight (5-7 m3/(h m2) @50Pa), either dMEV or natural ventilation can be used. MVHR is possible, too, as there are different reasons for the use of this technology, other than the air tightness of the building.
A problem arises when the measured air tightness of the building is very different from the target air tightness. In such cases often the ventilation strategy needs to be revised. What complicates the matter is that the air tightness test needs to be carried out when the building is finished. At this point remedial measures are very difficult to implement. E.g. the architect specified 5 m3/(h m2) @50Pa with natural ventilation and trickle vents. Now the trades have done a good job and the building achieved 2.5 m3/(h m2) @50Pa. This means MVHR needs to be retrofitted into the finished building.
Looking at the reality of the building industry, it is often difficult to predict the real air tightness of the building, as much depends on the workmanship of the trades. It is probably the better approach to plan for a solution that complies with the tighter standards, e.g. MVHR.
We find the best choice of ventilation strategy is MVHR – if it designed, specified, installed and maintained right. There are some cost implications, but the comfort and air quality will pay dividends (over and above the energy savings).
Alternative ventilation strategies:
dMEV is a much cheaper solution in the initial expenditure, but as these don’t recover any heat, with the expelled air all the heat energy is lost. Such fans are better versions of extractor fans, that run constantly on a low level and boost when necessary, e.g. when they detect increased humidity. Modern dMEV fans are very quiet.
recent research in Scotland has shown, that most dMEV systems do not deliver the desired indoor air quality? The reason is, that the ventilation path through the building is much less controllable than with MVHR systems. E.g. some bedrooms might have very little to nearly no ventilation at all. dMEV systems need to be carefully specified to avoid such downfalls of the system.
Natural ventilation via background (trickle) ventilators with mechanical intermittent extract fans is still an allowed ventilation strategy for ‘leakier’ houses, but…
that in practice hardly any new built house will achieve the legal requirements for indoor air quality, unless occupants open window regularly? As such natural ventilation alone is not fulfilling the demands of Building Standards and therefor it is not a viable ventilation strategy. Occupants need to co-operate, e.g. keeping windows of bedrooms in use tilted all night (without curtains or blinds blocking the ventilation path) and cross-ventilate during the day every couple of hours.