# Heating energy calculation methods Anti Hamburg Lecture TTK-UAS.

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Heating energy calculation methods Anti Hamburg Lecture TTK-UAS

1.Heating energy consumption 2.Electricity consumption 3.Cooling energy consumption 4.Hot tap water boilers energy consumption Basics about energy consumption 1

Energy efficiency regulations in EU countries Compareing consumption: 1.Primary energy 2.Final energy 3.Overall Net energy demand limit 4.Heating energy 5.Heating and cooling energy

Differences

Basics for heating energy calculations Envelope elements and materials Materials thermal conductivity Envelope areas Way of managing ventilation and airflow rate

Heat losses H BE = ΣU i ⋅ A i + ΣΨ i ⋅ l i U i – Envelope thermal conductivity, W/m 2 ⋅ K A i – Envelope area, m 2 ΣΨ i – thermal bridge conductivity, W/m ⋅ K l i – thermal bridge lenght, m H vent = ΣL ⋅ c ⋅ ρ ⋅ (1- f) ΣL– air change, m 3 /s C– air specific heat, 1005 J/kg ⋅ K ρ– air density, 1,2 kg/m 3 f– heat recovery efficiency H infilt = q i ⋅ c ⋅ ρ q i – air change, m 3 /s

Heating energy consumption calculating methods 1. Degree-days method (static method to analys annual energy use)

Degree-day for heating period Weather data for heating energy calculations In every region have own and also different weather data Degree-day shows how long period we should heat our houses Degree-day are used with balanced temperature

Different climate every region Illustrative picture

Balanced temperature and degree- day Balanced temperature is temperature where we have take away temperature increase from free heat Free heat temperature increase means mainly heat from people, electrical devices, lighting and free heat from sun If we can get lot of free heat on heating season then we have low balanced temperature

Balanced temperature Free heat Real need for heating Room temperature Calculated heating power Outside temperature Balanced point Outside temperature Days Need for cooling

Balanced temperature and heat losses Free heat temperature increase big when we have heatlosses through envelope and ventilation  Δt FH =Φ FH /H Calculateing balanced temperature is also important to know how big is or sould be indoor air temperature  t B =t IN -Δt FH

Balanced temperature and degree-day One degree day represents 1 ° C temperature difference between the estimated 24-hour period average internal ambient air temperature.

Estonian degree-days TBTB SUM

Heating energy consumption Q HL = H ⋅ S ⋅ 24 ⋅ 10 -3 Q HL – Heating energy useage, kWh/a H– Building specific heat conductivity, W/K S– Degree-days, °C ⋅ d 24– day, h H= H BE + H vent + H infilt H BE – Building envelopes H vent – Ventilation H infilt – Infiltration

Heating energy consumption calculating methods 2.Monthly average ambient outdoor temperature method (were used befor degree-days method)

Calculated enery usage Heating energy use per heating surface Degree days3974°C/d Balanced temperature=16.25 °C EnvilopeArea m 2 Estimated U ‑ value, W/(m 2 K) Estimated heat loss kWh/a Percentage Insulated exterior wall 739.460.2618337 12.3 Original exterior wall 867.000.2621500 Roof 762.960.2618920 5.9 Floor 762.960.2518192 5.6 New windows 468.21.6071448 22.1 Windows 17.021.602597 1.2 Exterior doors 8.361.601276 Volume m³Air exchange rate Estimated heat loss kWh/a Air exchange 8910 0.6170810 52.9 Σ323079 Heating energy use per heating surface 97.9 kWh/m2*a

Heating energy consumption calculating methods 3.Dynamic simulations (can be taken out of the current energy use is also best but difficult calculation method) Programs based on ISO 13790:2008 standard

ISO 13790:2008 standard ISO 13790:2008 gives calculation methods for assessment of the annual energy use for space heating and cooling of a residential or a non-residential building, or a part of it, referred to as “the building”. This method includes the calculation of: the heat transfer by transmission and ventilation of the building zone when heated or cooled to constant internal temperature; the contribution of internal and solar heat gains to the building heat balance; the annual energy needs for heating and cooling, to maintain the specified set-point temperatures in the building – latent heat not included; the annual energy use for heating and cooling of the building, using input from the relevant system standards referred to in ISO 13790:2008 and specified in Annex A.

Example

Heating energy usege as main point to achieve low-energy building We must know where we lose energy Which values we must know before we start to calculat heating energy usege Also what we need to have before when we start to make calculation.

Calculated enery usage Heating energy use per heating surface Degree days3974°C/d Balanced temperature=16.25 °C EnvilopeArea m 2 Estimated U ‑ value, W/(m 2 K) Estimated heat loss kWh/a Percentage Insulated exterior wall 739.460.2618337 12.3 Original exterior wall 867.000.2621500 Roof 762.960.2618920 5.9 Floor 762.960.2518192 5.6 New windows 468.21.6071448 22.1 Windows 17.021.602597 1.2 Exterior doors 8.361.601276 Volume m³Air exchange rate Estimated heat loss kWh/a Air exchange 8910 0.6170810 52.9 Σ323079 Heating energy use per heating surface 97.9 kWh/m2*a

Energy certificate

Low energy and nearly zero energy buildings

Free heat from sun It depens on windows solarfactor

Possibilities for saveing energy Through which part energy leave from house (throught envilops, exshausted ventilation air) 1.How big are envilopes thermal conductivitys 2.How big are envilopes area 3.What is ventilation air rate 4.What is the free heat load on building To get good analyses is needed to to take right building volumes from construction project and accurate data on the indoor climate.

Potential of energy efficiency Heating energy use per heating surface Degree days2542 Balanced temperature=12.28 EnvilopeArea m 2 Estimated U ‑ value, W/(m 2 K) Estimated heat loss kWh/a Insulated exterior wall+50 mm insultation 739.460.209023 Original exterior wall- 150 mm insulation 867.000.2010579 Roof762.960.209310 Floor-150 mm insultation762.960.209310 New windows-with 3 glasses468.21.0028565 Staircases windows- exchange17.021.001039 Exterior doors-exchange8.361.00510 Volume m³Air exchange rate Estimated heat loss kWh/a Air exchange with heat recovery (70%)8910 0.632779 Σ101115 Heating energy use per heating surface 30.6 kwh/m2*a

New energy certificate

Conclusion Good knowledge of indoor climate building physics, heating and ventilation ensures the quality of energy calculations.

Thank you!!