Type of heating

The type of heating used in dwellings is important for the total energy consumption, as well as for the total emissions to air of environmentally harmful gases. Three principal heating types are used in Norwegian dwellings:

• electric heating,

• wood-firing,

• oil-heating (paraffin and heating oils).

District heating accounted for less than 1% of the total energy consumption in the dwelling stock in 1990 (Rypdal, 1993), and is therefore neglected in this context. Other heating sources like gas and coal are also negligible.

Efficiency and pollution

Table 3.34. Air exchange rates (h-1) for the stereotypes of houses. Type of ventilation system is indicated in the parenthesis; (n) = natural ventilation system, (m) = mechanical ventilation system. Based on recommendations from Brunsell (1993).

Stereotype of house Year of construction

Before 1956 1956 to 1970 1971 to 1980 1981 to 1990

h-1 h-1 h-1 h-1

One-family houses 0.7 (n) 0.6 (n) 0.5 (n) 0.5 (m)

Divided small houses 0.6 (n) 0.6 (n) 0.5 (n) 0.5 (m)

The efficiency of the three heating types differ significantly. An efficiency of 100% may be assumed for electric heating, 75% for oil-heating in large boilers, and 65% for wood- firing (Ljones et al., 1992). The energy consumption of houses using firewood or fossil fuel as heating source will therefore be larger than if electric heating is used. Also, there are distinct differences between the quantity of pollution resulting from the use of the three principal heating sources. In the estimation model, only emissions of carbon dioxide (CO₂), sulphur dioxide (SO₂), nitrous oxides (NO_x) and particulate matter (PM₁₀) are accounted.

Norwegian electricity is 100% hydroelectricity. Therefore, no pollution is assumed resulting from the use of electricity for heating purpose.

The quantity of CO₂ emitted in the combustion of firewood and fossil fuels is determined by the carbon content of the fuel. In the photosynthesis, CO₂ is assimilated in bio-mass and bound as carbon. Thus, the emission of CO₂ from the combustion of firewood, equals the quantity of CO₂ bound in the wood during the growth of the tree. No emission of CO₂ is therefore accounted resulting from the combustion of firewood since firewood is a renewable energy source, and the emissions of CO₂ are included as a part of the natural carbon balance (SSB, 1993).

However, wood-firing results in some emissions of SO₂ and NO_x, and large emissions of particulate matter (PM₁₀) and carbon monoxide (CO). The large emissions of PM₁₀ and CO from wood firing are mainly caused by insufficient combustion in small ovens. In addition to the above mentioned emissions, wood-firing also involves some emissions of non-methane volatile organic compounds (NMVOC) and polycyclic aromatic

hydrocarbons (PAHs).

The use of fossil fuels involves emissions of CO₂, SO₂ and NO_x, as well as some particulate matter. Table 3.35 shows the amount of pollution associated with the three principal heating types used in Norwegian dwellings.

Table 3.35. Efficiency of heating systems and emissions of CO₂, SO₂, NO_x and PM₁₀ associated with the use of electricity, fuel oil and fire wood. The values are valid for 1990 (SSB, 1993).

Type of heating Efficiency Energy Density Emissions

content of fuel CO₂ SO₂ ** NO_x PM₁₀

GJ/ton tons/m3 kg/MWh g/MWh g/MWh g/MWh

Electricity* 100% - - 0 0 0

Fuel oil 75% 43.1 0.84 265 234 209 25

Firewood 65% 16.8 0.5 0 86 150 2143

* Norwegian electricity is produced from hydropower. ** Data on SO₂ from 1991.

Main heating source in Norwegian dwellings

The main heating source used in dwellings was reported in the Survey of Housing Conditions 1988 and the Residential Energy Use Survey 1990. Results from these surveys are shown in Table 3.36. Both surveys showed that electricity is the dominating heating source in Norwegian dwellings. The share of dwellings having electricity as main heating source, was lower in the Survey of Housing Conditions than in the Residential Energy Use Survey. However, it has to be noted that the results are based on

questionnaires and the inhabitants may not have been able to identify the relative importance of the different heating sources correctly. The importance of wood-firing is for instance often exaggerated since it is more demanding compared to electric heating.

Table 3.36. Main heating source in Norwegian dwellings in 1988 and 1990. Based on the Survey of Housing Conditions 1988 (NOS B892, 1990) and the Residential Energy Use Survey 1990 (Ljones et al., 1992).

Survey Main heating source

Electricity Liquid fuel Firewood Central heating Total

Survey of Housing Conditions 1988

One-family houses 41% 18% 35% 6% 100%

Divided small houses 64% 16% 16% 5% 100%

Large houses 59% 3% 5% 33% 100%

Residential Energy Use Survey 1990

One-family houses 49% 16% 29% 5% 100%

Divided small houses 77% 10% 8% 4% 100%

Type of heating in the stereotypes of houses

Based on empirical data, the yearly energy consumption used for heating purposes in dwellings has been distributed by type of energy source in Ljones et al. (1992). These estimations are used to distribute the calculated heating requirement of the stereotypes of houses on the different energy sources. Table 3.37 shows the shares of the calculated heating requirement of the stereotypes of houses covered by electricity, fuel oil and firewood. It is seen that electricity is presumed to represent an increasing share of the energy consumption used for heating for the newer houses. The share of fuel oil and firewood shows a corresponding decrease for these houses.

The values on type of heating shown in Table 3.37 are based on average values for the entire group of dwellings each stereotype of house represents. Such average values are not likely to be found in reality. For instance, in 1990, only 21% of the dwellings were reported having three alternative heating systems installed (Ljones et al., 1992). However, to estimate the aggregated energy consumption of the dwelling stock, average values have to be used to calculate the energy consumption of the stereotypes of houses.

A large share of the electricity used for lighting, cooking and equipment also contributes to space heating. How large this contribution is, depends on the heating requirement of the dwellings. The larger heating requirement of a dwelling, the more of the "free energy" is utilised for useful heating purpose. This implies that if the heating requirement of a house is reduced through for instance additional thermal insulation measures, a reduced share of the "free energy" will be utilised for useful heating purpose.

Table 3.37. Supplied heating consumption distributed on type of heating for the stereotypes of houses. Based on (Ljones et al., 1992).

Stereotype of house Electricity Fuel oil Firewood Total

One-family houses

Before 1956 50% 17% 33% 100%

1956 to 1970 47% 18% 35% 100%

1971 to 1980 47% 18% 35% 100%

1981 to 1990 61% 13% 26% 100%

Divided small houses

Before 1956 64% 16% 20% 100% 1956 to 1970 59% 18% 23% 100% 1971 to 1980 59% 18% 23% 100% 1981 to 1990 71% 13% 16% 100% Large houses Before 1956 56% 35% 9% 100% 1956 to 1970 69% 24% 7% 100% 1971 to 1980 69% 24% 7% 100% 1981 to 1990 78% 17% 5% 100%

The type of heating also influence the temperature control and temperature distribution in the dwellings. This may affect the average indoor temperature in dwellings and thereby influence the calculated heat loss. Small ovens may rise the temperature near the ovens and cause a non-uniform temperature distribution in the dwellings. Wood-firing may also be regarded being bothersome compared to electric heating and central heating systems. Central heating systems tend to give uniform temperature distribution in the dwellings. Therefore, neither central heating systems, nor wood-firing, are well suited for

controlling room temperatures individually.

On the other hand, electric heating, which is the main heating source in Norwegian dwellings, is well suited for controlling and regulating the indoor temperature. The temperature may easily be reduced in rooms which are not in regularly use. Most Norwegian houses are constructed as light timber framed houses with low thermal heat capacity. Therefore, the room temperatures may be raised rather quickly after being lowered for parts of the day or for the night, or for parts of the week. The average indoor temperature may therefore be expected being lower in electric heated houses compared to houses having central heating systems.

3.5.10 Indoor temperature

The indoor temperature is one of the most important parameters determining the energy consumption of houses. According to the Norwegian Standard 3031 (NS 3031, 1987), an indoor temperature of 22oC should be used when calculating the energy requirement of houses. However, the average indoor temperature in Norwegian dwellings in the heating season is probably lower than 22o_C.

Indoor temperatures in Norwegian dwellings

Statistics on indoor temperatures in Norwegian dwellings are limited. However, some information is found in the Residential Energy Use Survey 1990. The questionnaires of this survey asked for the total dwelling area and the heated area of the dwellings. The (approximately) indoor temperatures in the heating season in the living rooms, bedrooms and bathrooms should also be stated. The reported data are shown in Table 3.38. It should be noted that the temperatures are based on approximately values reported by the

inhabitants themselves.

In these questionnaires, 15oC was set as a distinction between heated and unheated space. The percentage of the dwelling area which was heated above 15oC is lowest for one- family houses, and highest for large houses. Concerning the reported temperatures in living rooms and bathrooms, no significant distinction can be drawn between the different types of dwellings. The average temperatures in the living rooms were in the range from 20.9o_{C to 21.6}o_{C, while the temperature in the bathrooms were in the range from 20.6}o_C

to 22.9o_{C. The indoor temperatures in the living rooms of Norwegian dwellings}

(including the bathrooms) may therefore be assumed being in the range from 21oC to 22oC.

The Norwegians prefer rather chilly bedrooms. Table 3.38 shows that the average temperature in bedrooms was reported to be only 14.1o_{C. Since the average temperature}

in the bedrooms is below 15oC, these rooms are defined as being unheated. The heat loss from the bedrooms may however be higher than the low temperatures indicate, since the bedroom windows often are open at night, reducing the thermal resistance of the outer constructions, and thus increasing the heat loss of the dwelling.

In the ERÅD-model developed by Energidata to estimate the profitability of various improvement measures in buildings, the basic indoor temperature in dwellings is set to be 21oC (Energidata, 1994). This basic indoor temperature is then adjusted according to the type of heating system, type of regulation system and heat capacity of the buildings. Further, the temperature in the bedrooms is assumed to be 5o_{C lower than the}

temperatures in the rest of the dwelling.

Table 3.38. Results from the Residential Energy Use Survey 1990. Average dwelling area, average heated area, heated area as percent of dwelling area, average indoor temperatures in living rooms, bedrooms and bathrooms, by type of house and year of construction (Nesbakken, 1995).

Type of dwelling Heated area Indoor temperatures

Dwelling area Heated area Heated area as % of dwelling area Living room Bathroom Bedroom m2 m2 oC oC oC One-family houses Before 1955 124.7 92.5 74% 21.4 21.4 13.9 1955 to 1970 115.0 94.3 82% 21.6 21.7 13.2 1971 to 1980 121.2 99.5 82% 21.4 22.2 13.6 1981 to 1990 133.2 114.6 86% 21.3 22.9 14.5 Total 123.6 99.6 81% 21.4 22.0 13.8

Divided small houses

Before 1955 92.6 78.6 85% 21.2 21.3 14.0 1955 to 1970 91.0 79.2 87% 21.6 22.5 14.9 1971 to 1980 89.3 77.3 87% 21.2 22.0 13.1 1981 to 1990 105.9 93.6 88% 21.4 22.6 15.0 Total 93.5 80.8 86% 21.3 22.0 14.2 Large houses Before 1955 66.2 61.4 93% 20.8 20.5 15.0 1955 to 1970 68.3 59.6 87% 21.1 20.6 15.1 1971 to 1980 67.0 58.8 88% 20.9 20.6 14.3 1981 to 1990 81.1 73.9 91% 21.2 21.8 15.0 Total 68.8 61.7 90% 21.0 20.7 14.9 Total 104.2 86.7 83% 21.3 21.7 14.1

Indoor temperatures in Swedish dwellings

Several surveys investigating the indoor temperatures of Swedish dwellings have also found average indoor temperatures below 22o_{C. In the most comprehensive survey, the}

indoor temperature was measured in more than 1364 dwellings (Norlén and Andersson, 1993). The average indoor temperature was found to be 20.9oC in one-family houses and 22.2o_{C in multifamily houses. The same survey also found lower indoor temperatures in}

older than in newer houses. The results from this survey agree well with other Swedish surveys9 _{which have measured the indoor temperatures to be between 20}o_{C and 21}o_{C in}

one-family houses, and approximately 1oC higher in multifamily houses.

However, for several reasons, results from Swedish surveys may not be directly adapted to Norwegian conditions. One reason is that the inhabitants in Norway normally pay the heating costs individually, while heating costs in Sweden to a larger extent are included in the rent. The inhabitants in Norwegian dwellings therefore have higher motivation for keeping the indoor temperature low, since this significantly influence the heating costs. As a result, the average indoor temperature may be assumed to be lower in Norwegian dwellings than in Swedish dwellings.

Another reason to be cautious when using Swedish data, is that central heating systems are common in Swedish dwellings, while electric heating systems are dominating in Norwegian dwellings. As mentioned earlier, higher indoor temperatures may be expected in houses with central heating systems than in houses with electric heating systems. For this reason, lower indoor temperatures may be expected in Norwegian dwellings than in Swedish dwellings.

In most of the Swedish surveys, the indoor temperatures have only been measured at one or two points, usually in the living room and in one additional room. The measured indoor temperatures may therefore not be representative for the entire dwelling. Indoor temperatures in the stereotypes of houses

Several Swedish surveys have found significant difference in the average indoor temperature in small one-family houses and large multifamily houses. In contrast, the Residential Energy Use Survey 1990 estimated the average temperature in Norwegian living rooms to be 21.3o_{C in both small and large houses (see Table 3.38). However, it}

should be noted that the Swedish data probably is more reliable than the Norwegian data since calibrated temperature meters have been used in the Swedish surveys, while the Norwegian data have been based on approximately indoor temperatures stated by the inhabitants themselves.

In the estimation model, the indoor temperature in the heated part of dwellings is presumed to be 21.0oC in detached one-family houses, 21.5oC in divided small houses, and 22.0oC in large houses. The temperature differences between the house types are in

accordance with the findings in the Swedish surveys, but not with the indoor temperatures estimated in the Residential Energy Use Survey 1990.

There are several reasons for assuming higher indoor temperatures in large houses. One reason is that a larger share of large houses have central heating systems (see Table 3.36). The indoor temperature in houses with central heating systems tend to be higher than in houses with other heating systems. In Energidata (1994), the basic indoor temperature is estimated to be approximately 2.0o_{C higher in houses having central heating systems than}

in houses having direct electric heating systems. A second reason for the higher indoor temperature in large houses is that the heating costs are often included in the rent for dwellings in large houses. The inhabitants thus do not have the same incentives for

reducing the heating costs by reducing the indoor temperature. A third reason is that large houses normally have a higher heat capacity compared to small wooden houses. The effect of reducing the indoor temperature for parts of the day or for night is smaller in the large houses because of this high heat capacity. A higher average indoor temperature can therefore be expected in the large houses. Finally, the area of the external constructions relative to the floor area is smaller for large houses than for small houses. The relative heat loss is therefore lower for large houses compared to small houses.

However, the thermal insulation level of the outer walls of old large brick- and concrete buildings is generally poorer than in old wooden houses. There is thus also a reason to expect the indoor temperature to be lower in large houses than in small houses.

A large share of the dwellings in Norway (especially detached one-family houses), have one or several rooms which are not regularly used. These rooms are therefore often not fully heated. In Table 3.38 it is shown that the average heated space of dwellings in Norway was 81% of the dwelling area for one-family houses, 87% for dwellings in houses in row and 90% for dwellings in large houses.

The effect of reduced temperatures in parts of the dwellings is taken into account in the estimation model by calculating a weighted average indoor temperature for the different stereotypes of houses. These weighted average indoor temperatures are calculated by presuming the temperature in the unheated parts of the houses (including the stair rooms) to be 15oC, and the temperature in the heated parts to be 21.0oC in detached one-family houses, 21.5oC in divided small houses, and 22.0oC in large houses. Table 3.39 shows the estimated heated area and the estimated average indoor temperatures of the different stereotypes of houses. The percentage of the dwellings which is heated above 15oC is based on information from the Residential Energy Use Survey 1990, referred to in Nesbakken (1995)