For a company that's only built five houses in the UK, Huf Haus has attracted plenty of interest. This German housebuilder is much admired for its contemporary design, its open-plan layouts and its use of prefabricated building elements. One lesser known aspect of the Huf Haus story is that the houses are fitted with warm air heating.
To the typical British homebuyer, warm air is a turn-off. It has never lived down its reputation, earned in the 1960s and 1970s, for being noisy, draughty and plain ineffective. Yet the technology has moved on considerably and in the USA it is now the predominant form of heating, partly because it combines well with summertime air conditioning.
In Germany, warm air is regarded as an aspirational choice, in a similar way to underfloor heating. Contrast this with the UK where our sole remaining manufacturer, Johnson & Starley, now concentrates on upgrading or replacing old systems in local authority housing; customers from the private sector being virtually unknown.
One of the last major private sector users of warm air was Leach Homes in Hertfordshire. After fitting many hundreds of Johnson & Starley units in the 1980s, they switched to wet systems. Derek Pearson, Construction Director of Leach Homes said: "We felt we had to switch because we were getting purchaser resistance. The installation was usually trouble free and I personally lived in a warm air house and enjoyed it but we simply couldn't afford to loose sales because of our chosen heating system."
Which is why Huf Haus' Peter Huf does not make a big splash about his preferred heating method. "When I talk to prospective customers in Britain, I can see them becoming worried when they learn how the houses are heated. It often takes me four or five sessions to convince them they are making a wise choice. But the feedback I get from people who have gone ahead with our warm air system is always very positive."
The heating systems used in Huf's houses are made in Germany by Schrag. Most warm air systems work by directly heating the air but the Schrag Comfort-Heating system works indirectly through heating hot water. One advantage of this method is that you don't need any additional heat source for the domestic hot water. You can also run towel radiators in the bathrooms. The warm air is ducted inside the floorspace and exits into the rooms via cast aluminium floor vents (measuring 100 mm x 300 mm), normally located under the windows. This provides for both warm underfloor heating and a hot air curtain in front of windows. There are a series of return ducts as well so that the air is always circulating gently. To work well, the Schrag system requires a near airtight envelope but having achieved that, then Schrag system is capable of delivering all heating and ventilation requirements and, if required, air conditioning as well.
One disadvantage of warm air is that the systems are fan driven and fans can be noisy. However, a Huf Haus is built with a utility basement and with 250 mm thick solid masonry floors so any fan noise is unable to penetrate the living space.
Harry Seward is an architect who built the UK's first Huf Haus. He has built with warm air systems in the past and needed little persuading to include the Schrag system in his current project. The house is divided into four heating zones and each zone is controlled by programmed thermostats. "The system is powered by a fan which has five settings: when a heat boost is needed, the fan speed increases automatically. Yet we are unaware of any additional noise and we are also unaware of any draughts. In summer, we continue to run the fan system which stops any overheating: we could have had a full air conditioning unit added to the system but thought it was probably unnecessary. The incoming air is drawn in through the basement: in winter, 85% of the warm air is recirculated and mixed with 15% fresh air, thus making it a very efficient system, more heat recycling than heat recovery. There are filters on the ducting which take out any pollutants like cigarette smoke and the air in the house always seems fresh."
With this level of control, the Schrag warm air system is not cheap. It is reckoned to cost about 20-30% more than a conventional radiator system, putting it on an equal footing with underfloor heating. But in projects which seek to combine heating with whole house ventilation and/or air conditioning, the cost penalty all but disappears. Schrag heating enquiries are handled in the UK via Huf Haus' offices but have a German language-only website at www.schrag.de.
Beyond Johnson & Starley's Janstar units and Schrag's Comfort Heating, there is nothing else available in the UK capable of providing a whole house warm air heating solution. There are several small businesses selling mechanical ventilation with heat recovery (MVHR) but these are designed to go on top of a heating system, not to replace one - they need a credible heat source in order to work in severely cold weather. Warm air units can be readily adapted to incorporate MVHR so it would seem logical to use warm air on the increasing number of super insulated homes being built which demand some form of mechanical ventilation. However, as yet, such thinking would seem to be restricted to the social housing sector.
Source
Building Homes
