Introduction

S. Robert Hastings

The success of the exemplary buildings presented in the previous section is the result of good design, but also of the capabilities of high-performance systems and components selected to work effectively together as a whole building/system complex. This section examines the systems which together make a high-performance housing project possible.

It begins with the building envelope, since providing a highly insulating and air-tight shell for the building is the first priority. When the envelope is very air tight, a ventilation system is essential to assure good air quality and to avoid excessive humidity problems and potential mould growth in winter. The next logical step is to incorporate a heat recovery system between the exhaust and supply air flows. In a highly insulated building, heating ventilation air requires a proportionally very large amount of energy. Modern heat recovery systems can recover 80 per cent or more of the heat otherwise lost in the exhaust air, minimizing this energy demand.

Once the heat demand is drastically reduced, the next challenge is to produce and deliver the heat efficiently, economically and with maximum comfort. The ventilation system can deliver heat as well as fresh air to each room. This is a standard solution in American homes, but new territory in many other countries. Housing with a very small heating demand is an ideal condition for air heating. Because so little heating power is needed, the volume of air needed for hygiene reasons is sufficient to deliver the needed heat at temperatures below 55°C. This minimizes the noise of the air flow and the smell of burned dust which occurs at higher temperatures. Last, but hardly least, the double use of the ventilation system and elimination of the need for another system saves construction and operating costs.

The next logical issue is the origin of the heat. The most ecological source is the sun. Solar water and air collector systems are mature, reliable solutions. Both offer the advantage of being able to supply heat for space heating and domestic water heating. The latter represents a large fraction of the total energy demand of very low energy housing. But solar thermal systems must be considered 'backup systems'; a primary system is still needed. Indirect solar use in the form of biomass (primarily wood or wood pellets) is a good primary supply system. Another indirect source is an earth-to-air heat exchanger which in winter draws on the solar energy naturally accumulated in the ground over the summer. District heating where the heat is produced from burning refuse can also be termed a renewable energy source, given the inevitability of humans producing refuse. Other heat production systems are also examined, including less ecological or sustainable solutions, to allow a more comprehensive comparison for selecting a system. Many of the heat production systems could be operated more efficiently if there were an effective means to store heat, be it for a few days or a season. Two types of heat storage are reviewed, sensible and latent heat storage.

Given its very high primary energy values, electricity is a key topic. Accordingly, adding photovoltaic electric generation can dramatically reduce the total primary energy balance of such housing. Similarly, selecting appliances with low energy consumption is only sensible. A saved kWh of electricity is magnified by the primary energy factor, in this book 2.35 for the non-renewable part of electricity generation. Hence, a high efficiency refrigerator, dish washer, washing machine and range; as well as efficient fans, pumps and controllers for the technical systems of the house result in a major reduction in the total primary energy balance.

This section ends with a technology looking to the future but available today, building information systems. Such systems can not only offer optimized control and performance of the technical systems of a house, but also convenience, comfort and security for the occupants.

Indeed, very low energy housing is building looking to the future. Not only does it help slow the rate of depletion of non-renewable resources, it offers better comfort. The key, as mentioned in the opening, is to select highly efficient systems which work well together and as part of a whole, sustainable building concept.

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