Has anyone else come across heat recovery giving very good results in their model that are higher than expected. In a heating dominated climate, we have a PSZ system serving 5 zones, with baseboards used to meet heating loads in the slave zones (they've been hard sized to just get the unmet hours in an acceptable range).
I have broken down an analysis of building heating energy by month, from LS-D and SS-D. Assuming the SS-D account for all 'building' loads (envelope, infiltration, lights, etc), and SS-D is all that, plus the OA load. For a 50% effective ERV (and no additional fan heat), I get the following for winter months:
Monthly Heating Energy Used (MBTU)
Envelope Loads (LS-D) no ERV
Envelope and OA energy (SS-D) no ERV
Envelope and OA energy (SS-D) with ERV
Envelope energy as % of total (LS-D/SS-D) no ERV
Reduction of energy in SS-D due to ERV (at 50% eff)
J
126
222
154
0.5676
0.306
F
112
196
135
0.5714
0.311
M
90
157
101
0.5732
0.357
A
54
82
47
0.6585
0.427
O
37
52
27
0.7115
0.481
N
67
112
70
0.5982
0.375
D
108
187
127
0.5775
0.321
E.g. in January a 50% eff ERV gives a 30% reduction in heating energy, even though the 'building' pre-OA accounts for 55% of the total energy. My gut feeling is that the 55% is not accurate and it is actually lower, but I can't convince myself using the reports.
Fiddling with the heat recovery control schemes doesn't seem to change the heating results by much either, however changing the effectiveness has a big impact to the results. In comparison, improving the wall performance has a relatively small impact.
I should say that this is a preliminary model so no design drawings available, and it a retail space with about 0.18 cfm OA/sqft.
Adam Barker, MBSc, C.E.T., LEED AP BD+C
Energy Project Manager
Provident Energy Management Inc.
T: 416-736-0630 x 1874 | abarker at pemi.com
