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METHOD TO SIZE ERVs and HRVs
Ventilator Sizing
Tables 1 and 2 should be used to determine the required airflow for a home. These guidelines are taken from ASHRAE
Table 1 – Ventilation Air Requirements, cfm
FLOOR |
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| BEDROOMS |
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AREA (ft2) |
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| >7 | |||||
<1500 | 30 | 45 |
| 60 |
| 75 | 90 |
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45 | 60 |
| 75 |
| 90 | 105 | |
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60 | 75 |
| 90 |
| 105 | 120 | |
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75 | 90 |
| 105 |
| 120 | 135 | |
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90 | 105 |
| 120 |
| 135 | 150 | |
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>7500 | 105 | 120 |
| 135 |
| 150 | 165 |
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Table 2 – Ventilation Air Requirements, L/s
FLOOR |
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| BEDROOMS |
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AREA (m2) |
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| >7 | |||||
<139 | 14 | 21 |
| 28 |
| 35 | 42 |
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21 | 28 |
| 35 |
| 42 | 50 | |
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28 | 35 |
| 42 |
| 50 | 57 | |
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35 | 42 |
| 50 |
| 57 | 64 | |
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42 | 50 |
| 57 |
| 64 | 71 | |
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>697 | 50 | 57 |
| 64 |
| 71 | 78 |
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/ HRV
HEATING AND COOLING LOAD CHARTS
Although the ventilators process the outside air before it enters the home, additional heating and cooling loads need to be considered.
ERV
HEATING LOAD BTUH
Outside |
| Heating Load (Btuh) @ |
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| Inside Design Temp 72°F |
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Temp °F |
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ERV1150 | ERV1200 | HRV1150 | HRV1250 | ||
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5186 | 8143 | 6636 | 10603 | ||
4919 | 7723 | 6294 | 10057 | ||
5075 | 7967 | 5952 | 9510 | ||
4783 | 7509 | 5610 | 8964 | ||
4491 | 7051 | 5268 | 8417 | ||
0 | 4200 | 6594 | 4925 | 7871 | |
5 | 4234 | 6647 | 4583 | 7324 | |
10 | 3918 | 6151 | 4241 | 6777 | |
15 | 3958 | 6214 | 3899 | 6231 | |
20 | 3611 | 5669 | 3557 | 5684 | |
25 | 3264 | 5124 | 3215 | 5138 | |
30 | 2916 | 4579 | 2873 | 4591 | |
35 | 2569 | 4034 | 2531 | 4045 | |
40 | 2222 | 3489 | 2189 | 3498 |
The heating load chart shows the heating loads in Btuh for a range of winter design temperatures for each model of ventilator.
EXAMPLE: The heating design temperature for Little Rock, AR is 20_F. The additional heating load of the ERVBBLHA1200 at 20_F is 559 Btuh. This additional load should be taken into consideration when sizing the heating equipment.
COOLING LOAD BTUH
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Outside | Cooling Load (Btuh) @ Inside Design Temp | ||||
72°F and 50% Relative Humidity | |||||
Enthalpy | |||||
Btu/lb | ERV1150 | ERV1200 | HRV1150 | HRV1250 | |
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30 | 380 | 640 | 670 | 1071 | |
31 | 618 | 1040 | 1090 | 1741 | |
32 | 855 | 1441 | 1509 | 2411 | |
33 | 1093 | 1841 | 1928 | 3080 | |
34 | 1331 | 2241 | 2347 | 3750 | |
35 | 1568 | 2641 | 2766 | 4419 | |
36 | 1806 | 3041 | 3185 | 5089 | |
37 | 2043 | 3441 | 3604 | 5759 | |
38 | 2281 | 3842 | 4023 | 6428 | |
39 | 2519 | 4242 | 4442 | 7098 | |
40 | 2756 | 4642 | 4861 | 7767 | |
41 | 2994 | 5042 | 5280 | 8437 | |
42 | 3231 | 5442 | 5699 | 9107 |
The cooling load chart shows loads in Btuh as well. To use the cooling load chart, first find the design enthalpy from a psychrometric chart using the design dry bulb and wet bulb temperatures. The cooling load can then be found for a range of enthalpies for each ventilator.
EXAMPLE: The design dry bulb temperature for Miami is 90_F and the average wet bulb at that temperature is 77_F. Using the psychrometric chart, the enthalpy is about 40.5 Btu per pound (Btu/lb) of dry air, which would round up to 41 Btu/lb dry air. In the left column, at 41 Btu/lb dry air, the ERVBBLHA1200 has an additional cooling load of 5042 Btuh, while the HRV1150CFM unit has an additional cooling load of 8437 Btuh.
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