Family house in Jeseník

Building description: the building of a family house is situated in Jeseník – the town of the FENIX Trading spol. s r.o. company’s headquarters. It is a prefabricated construction - SOLO Line 117 type manufactured by the RD Rýmařov s.r.o. company.

The speed of construction is one of the characteristic features of prefabricated buildings. The construction of this house started on July 19, 2007 (on the prepared baseplate) and during unbelievable period of two days the shell was ready and on July 27, 2007, after only one week of constructing works, the facade was finished.

Heating
The house is fully heated by an electric convector system. There is floor heating on the ground floor. In rooms with ceramic flooring there are Ecofloor heating mats placed in a layer of bonding cement directly under the tiling. The installation consists of atypical mats – made to the exact measure of the rooms by the Fenix company. Atypical mats are by circa 20% more expensive than common types, however this higher investment returns many times by the substantially easier and quicker – i.e. cheaper – installation.

In the living room there is laminated floor and therefore the Ecofilm heating films were chosen. The heating films are placed directly under the laminated flooring, which is a great advantage as the system reacts flexibly to any temperature changes – no matter if the change is initiated by the user or another factor, e. g. sunshine in the room. Another considerable advantage is – in particular with prefabricated constructions – that the films are installed by a “dry process”, i. e. without laying any concrete or cement. The installation is substantially faster and simpler and it is immediately possible to lay down the laminated flooring and put the system into service.

On the first floor there is carpet flooring and that is why the investor decided to use electric convectors for heating. In bathrooms the floor heating is completed with ladder radiators which improve the temperature starting dynamics and also function as towel dryers.

Regulation
The heating is controlled by the central regulation made by the BMR company. This regulation enables to maintain a desired temperature in rooms according to a set programme. For each room it is possible to set different temperatures and changing times. Programming may be carried out from one place through the controlling unit; the set programmes can be however entered through digital sensors in selected rooms. The user can operatively adjust the desired temperature in the room without changing the programmed heating mode. The adjustment is cancelled by the next programme change of temperature.

The regulation is very precise; it uses pulse width modulation to reach the programmed temperatures thanks to which the rooms are heated on the desired temperature and overheating does not occur. The regulation is completed with so called reducer of current load HJ 306 manufactured by the BMR company. This device controls the main output by gradual two-level switching of single heating circuits and prevents exceeding the output of the main circuit-breaker. This enables to use a main circuit-breaker with a lower value than would correspond to the sum of electrical appliances used in the building. With regard to the actual connecting fees for electric supply mains (500,- CZK/1A) the economic return of the device is immediate and at the same time the monthly payments are reduced.

Technical data
The building without cellar has two floors with a built-up area of 122,84 m² and heated area of 186,7 m² (ground floor-106m²; 1st floor-80,7m²). Heat losses were calculated on circa 10,5 kW, which with the heated area of 186,7 m² corresponds to the loss of 56 W/m² = circa 22,5 W/m³ (average headroom 2,5m).

Built-up area: 122,84 m²
Heated area: 186,7 m²
Calculated heat loss: 10,5 kW
Installed heating input: 13,4 kW
- ECOFLOOR heating mats: 4,7 kW
- ECOFILM heating films: 2,6 kW
- electric convectors: 5,3 kW
- ladder radiators in bathrooms: 0,8 kW
Main circuit breaker: 3 x 32 A
Electric supply rate: D45

The whole system is overrated by circa 25% against heat losses because the floor heating stresses comfortable heating of whole floor surface and with convectors the next higher output was selected because of heat loss. Thanks to the precise regulation and the above mentioned current load reducer this fact has no substantial influence on either main circuit breaker or heating system operating costs.

Heating system purchase costs

 
Operating costs
The building has been in constant use only since October 2007 and therefore there are not any relevant electricity consumption data available. The estimated payment for annual electricity consumption is about 25.000 CZK. The building will be observed and the consumption data will be continuously completed.
For an accurate assessment of energy consumption for heating was installed in addition to the building sub-meter.

Reasons for selecting the heating system
Prefabricated construction parameters are close or equals to the criteria set for Low Energy houses. Low consumption of heat for heating is a typical feature of these constructions and therefore it is necessary to consider carefully the selection of heating system. If you need relatively little heat for heating a house, the price for 1 kWh stops to be deciding and purchase and operating costs and the system regulation possibilities start to be very important. The systems which boast about the low price for 1 kWh of heat are usually the ones with the highest purchase costs. For majority of respondents the answer for question What are the most economical sources of heat production? would be a condensing boiler or heat pump. On the contrary electric convector systems are from the viewpoint of price for 1 kWh of heat denoted as cheap ones by hardly anybody. However these systems are comfortable, featuring excellent regulation and good purchase costs.

Low purchase costs, good regulation and low heat consumption of the building – these are the factors which in overall evaluation move electric convector systems in front of media-promoted heat pumps or condensing gas boilers.

Comparison
The electrical heating for this building including the central regulation costs 120.000 CZK incl. VAT. The estimated annual costs for energy are 25.000 CZK. Hot water system (floor heating on the ground floor, radiators on the 1st floor) with a heat pump would cost circa 300.000 CZK for the building. The estimated annual costs for energy are circa 15.000 CZK.

The annual savings for energy are theoretically only 10.000 CZK. It is not little. However the purchase costs for a hot water system were higher by 180.000 CZK. It means that in 18 years the operation of a heat pump will compensate only the system purchase costs. The question is if a compressor, vaporizer, pump and other heating system components survive the whole 18 years. The economic return of the system decreases with other investments and de facto fails.