Approximate calculation of heating expenses

To calculate approximate heating costs we use following data:1) Inside temperature – +22 oC2) Average annual outside temp. – 0 oC (from LBN 002-01)3) Duration of heating period – 203 days (from LBN 002-01)4) Price of heat – 45 Ls/MWh (including VAT, according to approximate „Rīgas Siltuma„ data)5) Buildings Nr. 1 heated residential area is 2124,2 m2, total heated area is 2733,0 m2 and occu-

pants will pay for common areas proportional to their living floor space6) Areas of external constructions:

a) Walls – 1614,0 m2

b) Windows – 510 m2

c) Doors – 15,5 m2

d) Roof – 767 m2

e) Floor – 803 m2

7) U-values of constructions:a) Walls – differb) Windows – differc) Doors – 1,8 W/(m2*K)d) Roof – 0.22 W/(m2*K)e) Floor – according to zones (0.48, 0.23, 0.12, 0.07 W/(m2*K))

Example of heat loss and price calculation due to heat transfer:a) First we calculate U- value:

Wall is made of FIBO block with constant thickness of 250 mm with heat conductivity value of λ=0,20 W/mK and variable insulation thickens with heat conductivity value λ=0,037 W/mK. We calculate U-value for different insulation thickness. Results are as follows:

1) With 100 mm insulation – U=0.244 W/(m2*K)2) With 120 mm insulation – U=0.215 W/(m2*K)3) With 180 mm insulation – U=0.160 W/(m2*K)

b) Secondly we calculate heat losses due to transmission:Q= (tins-tout)*A*U*(1+n1*n2*n3)Where: tins – inside temp. (Co)

tout – outside temp. (Co)A – area of construction (m2)U – heat transfer of construction (W/(m2*K))n1 – additional coefficient according to orientationn2 – additional coefficient according to windn3 - additional coefficient for other loses

Q= (tins-tout)*A*U*(1+n1*n2*n3) = (22-0)*545*0.244*(1+0*0.1*0)=3218 WAs reserve we multiply this by 1.1 getting Q=3218*1.1=3540 W

SIA “MEP solutions”Juridiskā adrese: Rūpnīcas iela 4-4, Rīga, LV-1015| Reģ.Nr. LV40103740050 | Būvkom. nr.: 11251 || www.mep.lv | solutions@mep.lv |

c) This calculation is done for all external constructions (walls, roof, windows, floor and doors)Total heat losses for Building 1 is calculated as – 44226 W or 44,23 kW.

d) Next we calculate heat losses from building for design year:Qyear = Q*Hd*24 Where: Hd – heating days

24 – hours a dayQyear = 44,23*203*24=215488 kWh/year or 215,49 (MWh/year)

e) Calculation of expenses:P =Qyear *MWhere: M – price of heat (Ls/MWh)P=215.49 *45=9697 (Ls/year)If we divide this with live residential area we get: 9697/2124=4.57 (Ls/m2/year).Further if assumed that 203 is about 6,77 months than price for heating would be:4.57/6.77=0.68 (Ls/m2/year)

Price of heating (Ls/m2/year) at different insulation thickness and window type:Insulation thickness (mm) 100 120 180Window type and U-value

Double glazed (U=1.4) 4.57 4.43 4.17Tripple glazed (U=1.1) 4.13 3.99 3.73Tripple glazed (U=1.0) 3.98 3.84 3.59Tripple glazed (U=0.9) 3.84 3.70 3.44

Price of heating (Ls/m2/month) at different insulation thickness and window type:Insulation thickness (mm) 100 120 180Window type and U-value

Double glazed (U=1.4) 0.68 0.65 0.62Tripple glazed (U=1.1) 0.61 0.59 0.55Tripple glazed (U=1.0) 0.59 0.57 0.53Tripple glazed (U=0.9) 0.57 0.55 0.51

These calculated expenses are approximate and don’t take into account internal or solar heat gains as well as heat necessary for ventilation air.

Made by:Jurģis Zemītis

“MEP solutions”design engineer

SIA “MEP solutions”Juridiskā adrese: Rūpnīcas iela 4-4, Rīga, LV-1015| Reģ.Nr. LV40103740050 | Būvkom. nr.: 11251 || www.mep.lv | solutions@mep.lv |