Articles and whitepapers

Going Green with HVAC (4/6/2007)

By Dave Robinson, Sensible Heat

First, a few facts; around a third of the CO2 emissions produced by the UK come from energy used in domestic dwellings. Of this energy, about 66% is used for space heating, and a further 18% is used to heat domestic hot water. The rest is used by domestic appliances, lighting etc. From these simple statistics, we can see that if we want to tackle the problem of CO2 emissions, energy used by HVAC (heating, ventilation, air conditioning) equipment is a very important factor.

Homeowners are now becoming increasingly aware of the issues, and are demanding 'green' technology in their homes. Unfortunately, they are faced with a plethora of conflicting and sometimes misleading information from the burgeoning green industry. As a consequence, if you ask a homeowner for their 'top ten' green technologies, they may well come up with some inappropriate choices. So, how can we help them?

Technology for saving energy

Technology for saving energy (and thence CO2 emissions) in the home can be split into three categories:

1) Things for letting as little energy as possible escape into the environment (e.g. insulation, draughtproofing, and heat recovery ventilation).
2) Things for generating heat efficiently (e.g. condensing boilers, ground-sourced heat pumps).
3) Things for controlling the usage of the heat (e.g. modern HVAC controls).

These three categories should always be tackled in this order, taking care of the 'boring' insulation and air-tightness of the house first.

The second category is often mis-specified by the enthusiastic green early adopter, maybe swayed by fashion. Micro wind turbines, always high on the public's green top ten, are in fact almost always useless in an urban environment like Notting Hill! Solar PV (photo voltaic) arrays, another popular choice, are very expensive to install, generate power when you don't need it (i.e. during the day rather than at night when you need to use your lights), and have a questionable manufacturing eco footprint.

Conversely, the 'old fashioned' solar thermal panels for domestic hot water generation are usually a very good idea, with a 5-7 year payback, low manufacturing impact, and mature technology. Boring, but true! Also, for a house on mains gas, a modern condensing boiler is almost certainly the most eco-friendly heat generating device available. Again, this is hardly exciting dinner-party conversation, but it happens to be true. So, confusion abounds, but increasing amounts of money are being spent in this area, and not always on the right things!

The third category, controlling the amount of energy used in the house, is currently the real 'Cinderella' area, and is under-appreciated by contractors, specifiers and homeowners alike. By using modern HVAC controls, we can trim anything between 15% and 35% from the energy consumption of a typical home. This is done by using a number of techniques. Firstly, better temperature regulation avoids overheating - remember that a 1 degree reduction in temperature roughly equates to a 10% energy saving.

Accurate and targeted

Modern controls have advanced control algorithms, replacing the discontinuous on/off operation of a conventional thermostat with continuous control. Temperature 'cycling' is eliminated, resulting in improved comfort as well as energy savings.

HVAC controls can also be used to increase the zoning of the heating, from the current upstairs/downstairs two-zone arrangement to the ultimate of one zone per room. This allows rooms to run at different temperatures, and also unused areas of the house can run at much lower temperatures.

A Honeywell Hometronic radiator controller can easily be retrofitted to turn each room into a zone with accurate temperature control

Such controls can also be used to shut down the whole house to a low temperature when unoccupied, and to be automatically boosted back to comfort conditions before the occupants return - which is especially important with underfloor heating.

Retrofitting and designing for the future

Modern HVAC controls, especially wireless systems, can be retrofitted to virtually any house. The UK builds around 200,000 new homes every year, but what about the 23 million already-built housing stock? Many older houses cannot easily be fitted with better insulation, but all of them could benefit from proper HVAC controls.

Suppliers of other electronic systems for the house should take note; HVAC controls are the only electronic 'smart' technology that has a payback, both in monetary and environmental terms. Many projects slip by without this important area being addressed, and this can result in the customer being disappointed with their finished property, because opportunities to make the house more energy efficient, and more comfortable, were missed by the professionals advising them. Is a client likely to recommend a practise or contractor that has built them an old-fashioned property?

The Hometronic Manager wireless HVAC control user interface can be fitted anywhere

Conclusion

As the market for eco-friendly products expands and begins to mature, specifiers and contractors need to embrace new technologies. Professionals need to get themselves educated; bodies such as CAT (Centre for Alternative Technology) and The Green Register of Construction Professionals can provide informed, unbiased advice and training.

Our planet is warming up. Unchecked, it will soon become uninhabitable. We can help to do something about this, and at the same time run profitable businesses delivering what our customers are demanding. Isn't that sensible?

Dave Robinson is the Managing Director of Sensible Heat, manufacturer of HVAC controls and integration products, distributor of the Honeywell Hometronic wireless home automation system, and green energy consultant.

www.sensibleheat.com