2021
Up and Running with the Passive House Planning Package (9.7 IP) Module 2 | Class 4 | Fresh Air Ventilation
bldgtyp | NYPH
Q: How do you calculate the winter heating energy demand? A: (QT + QV) - η
Transmission + Ventilation LOSSES
(QS + QI)
Solar + Internal GAINS
bldgtyp | NYPH
NYPH: Up and Running with PHPP
1
2021
Q: How do you calculate the winter heating energy demand? A: (QT + QV) - η
(QS + QI)
Transmission, done!
bldgtyp | NYPH
Q: How do you calculate the winter heating energy demand? A: (QT + QV) - η
(QS + QI)
Solar Gain, done!
bldgtyp | NYPH
NYPH: Up and Running with PHPP
2
2021
Q: How do you calculate the winter heating energy demand? A: (QT + QV) - η
(QS + QI)
Ventilation Losses?
bldgtyp | NYPH
Q: How do you calculate the winter ventilation losses? A: QV = Vv
nv
CAir
GWINTER
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NYPH: Up and Running with PHPP
3
2021
Q: How do you calculate the winter ventilation losses? A: QV = Vv 'Ventilated Volume’ (ft3)
nv
CAir
GWINTER
Volumetric Specific Heat Capacity of Air at Normal Pressure
Analysis Period Heating Degree Hours
(a constant = 0.018 Btu/ft3-F)
(KFhr / period)
[0.33 Wh/m 3-k]
bldgtyp | NYPH
Q: How do you calculate the winter ventilation losses? A: QV = Vv
nv
CAir
GWINTER
’Energetically Effective’ Air Change Rate (ACH)
bldgtyp | NYPH
NYPH: Up and Running with PHPP
4
2021
nv
nv = Air Infiltration ACH + Ventilation System ACH
The ACH due to air leakage through the envelope at ‘normal’ pressure (~4Pa)
The ‘Unrecovered’ airflow through the ventilation system (HRV/ERV)
bldgtyp | NYPH
nv
nv = Air Infiltration ACH + Ventilation System ACH = e × n 50 × (V n50 / V v)
bldgtyp | NYPH
NYPH: Up and Running with PHPP
5
2021
nv
nv = Air Infiltration ACH + Ventilation System ACH = e × n 50 × (V n50 / V v)
Volumes Wind Screening Factor Tested ACH at 50Pa
bldgtyp | NYPH
Volumes ? Vn50: Tested (Internal) Volume In the EN13829 standard, the internal air volume is given as follows: “The internal volume, Vn50, is the volume of air inside the measured building or part of building. The internal volume is calculated by multiplying the net floor area with the actual net ceiling height. The volume of furniture is not subtracted.” Vv: Ventilated Volume For residential buildings, in order to better compare the different air exchange rates in dwellings, multiply the TFA by a standard 8.2ft (2.5m) to calculate the Ventilated Volume. For Non-residential buildings, use the actual ceiling height.
bldgtyp | NYPH
NYPH: Up and Running with PHPP
6
2021
bldgtyp | NYPH
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NYPH: Up and Running with PHPP
7
2021
n50
bldgtyp | NYPH
nv
nv = Air Infiltration ACH + Ventilation System ACH
The ‘Unrecovered’ airflow through the ventilation system (HRV/ERV)
bldgtyp | NYPH
NYPH: Up and Running with PHPP
8
2021
nv
nv = Air Infiltration ACH + Ventilation System ACH
n v-system
(1-η HR )
bldgtyp | NYPH
nv
nv = Air Infiltration ACH + Ventilation System ACH
n v-system
(1-η HR )
Avg. period ACH of the Vent. System Heat-Recovery effectiveness (%) of the Vent System bldgtyp | NYPH
NYPH: Up and Running with PHPP
9
2021
‘Extra’ Airflow in Summer
bldgtyp | NYPH
PHI recommends that the effective summer ventilation flow rate be ~50% higher than the winter ventilation flow rate. In most climates this will ensure hygienic conditions and lower cooling energy demand. In many climates, operable windows can be used to increase the effective ventilation rate in summer.
PHPP Allows you to specify one of three ‘types’ of summer ventilation system (or a combination): 1. HRV/ERV: As in a typical winter scenario, the fresh air is supplied through a mechanical ventilation unit and a balanced amount of extract air is removed. 2. Extract Air: An exhaust only fan 3. Window Ventilation: Using operable windows to ensure enough summer fresh air bldgtyp | NYPH
NYPH: Up and Running with PHPP
10
2021
‘Extra’ Airflow from the Ventilation System
bldgtyp | NYPH
‘Extra’ Airflow from Windows
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NYPH: Up and Running with PHPP
11
2021
So…. To calc. the ACH of the Air Leakage, we need: -
The Volume(s)
-
The tested ACH (@50Pa)
-
The ‘Exposure’ class
Then, to calc. the ACH of the Vent. System we need: -
The avg. period ACH of the system
-
The Heat Recovery effectiveness of the system
Then we add in ‘extra’ airflow for the summer period bldgtyp | NYPH
NYPH: Up and Running with PHPP
12