Consider a heated manufacturing shop with a total conditioned volume of 1,000 m^3. A measurement of the air leakage characteristics of the shop showed an infiltration rate of 1.5 ACH. Determine the energy savings due to caulking and weatherstripping improvements of the exterior envelope of the

Question

Consider a heated manufacturing shop with a total conditioned volume of 1,000 m^3. A measurement of the air leakage characteristics of the shop showed an infiltration rate of 1.5 ACH. Determine the energy savings due to caulking and weatherstripping improvements of the exterior envelope of the facility to reduce air infiltration by half. Assume the shop is located in Seattle, Washington and is heated by a gas-fired boiler with a seasonal efficiency of 80 percent.

Accepted Answer

To determine the energy savings due to the addition of insulation, we assume that the annual heating degree-days before and after the retrofit remain unchanged and are close to 18°C. For Seattle, the degree-days (with base 65°F or 18°C) are about 2,656°C-days.

The existing air infiltration has an equivalent UA-value of [latex]UA_{inf} = mc_{p,a}[/latex] = 500 W/°C. From Eq. (6.21) with the new air infiltration the equivalent UA-value 250 W/°C and the heating system efficiency set to be 80 percent (gas-fired boiler), the energy savings are calculated to be:

[latex]DE_{H,R} =E_{H,E} -E_{H,R}=\frac{24.(BLC_{E}.DD_H (T_{B,E})-BLC_{R}.DD_H (T_{B,R}))}{h_{H}}[/latex] (6.21)

[latex]ΔE=\frac {24}{0.80}.[(500-250)W/°C]*2656°C.day/yr=19.920kWh/yr[/latex]

The cost of caulking and weatherstripping is estimated to be about $1,500 (if only material costs are included). For a gas price of $0.05/kWh, the payback period for reducing the infiltration rate can be estimated to be:

[latex]Payback=\frac{\$1,500}{19.920kWh/yr*0.05\$/kWh}[/latex]=1.5 years

Therefore, the caulking and weatherstripping can be justified based only on energy cost savings. Additional benefits of reducing infiltration are improved thermal comfort.

Question 6.5: Consider a heated manufacturing shop with a total conditione...

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