HVAC Brief

Climate Conditions:
Risan has an annual rainfall of about 300cm, usually in short intense periods. Humidity generally is a major problem, with widespread damp evident, especially in unoccupied buildings. Our site is about 500m from the sea, and 60m above mean sea level.

Summer temperatures go into the 40s, though the historical average maximum is 29°C. Direct sun heat is obviously very much higher. Winter temperatures can fall to zero, but only for a few days; historical average minimum is 6°C.

Total annual solar irradiation is 1600kWh/m2; diffuse irradiation 600kWh/m2.

Passive House considerations:
The ‘normal’ Passive House methodology, designed for central European requirements, states that the heating requirement can be met only by the heat generated by the occupants augmented by pre-heating the in-coming ventilation air (with heat-recovery of the exhaust air).

Such a system, based only on the ventilation air, cannot meet the cooling load needed in the much warmer Mediterranean climate of Risan.

Another question is if such a system can cope with the dehumidification load.

Our requirements:
We need domestic hot water, and an energy-efficient system to provide winter heating, summer cooling, as well as dehumidification. Integrated control of the overall system is desirable. Mechanical ventilation is desirable.

Potential solutions:
One possibility is to use a passive house ventilation system for heating, possibly also for dehumidification, with a separate system for cooling.

Another possibility is using air-to-air heat pumps, reversing the operation to switch from heating to cooling. Ground source heat pumps would be more efficient for cooling, but the area of the site might not allow their use.

Solar panels are a logical method for water heating, but will need a back-up for times when there is no sun. This means electricity as there is no gas supply, and we do not want the dust and storage involved with solid fuel.

If a heating system is needed, we prefer underfloor to wall piping using water not electricity.

We foresee installing photo-voltaic in future when the cost of PV-produced electricity becomes cheaper.

General Description of the Site and Building

The site is roughly triangular, with one side running northeast to southwest, and the remaining sides running roughly north to south and southwest to south along roads to the southern point of the triangle. The east road is an old footpath now mainly blocked by undergrowth; the western one is a single-vehicle wide asphalt public road. Total site area is 380m2. The roads at the southern end are 3m lower in height from the northern end.

The building is a simple one-family house on 2 floors, each of 80m2 gross & internal space about 60m2 nett; internal ceiling height 2.70m. External dimensions are 10m x 8m with the 10m sides facing northeast and southwest. The roof is a two-sided pitch, with the centre line along the 10m dimension of the building. The space immediately under the roof is only usable for limited storage and access for maintenance.

The main living areas are oriented to the southwest. Glazing on the south-west side is slightly less than 40% of the wall surface, and there is a large overhang both of the roof and of the top floor balcony to shade the walls beneath them.

On the southwest side, there is vehicle access from the public road and parking, with a wall for static support of the house. On the parking level alongside this wall there will be storage rooms, one of which will be for technical equipment such as HVAC, pumps &c.

© all text and photographs, except where individually credited to other sources: James Collins