Summary of the alternative ventilation strategies
| Alternative | Operation | No. of users | Alteration work | Benefits | Downsides |
|---|---|---|---|---|---|
| Alternative 1 (A1) | Natural ventilation in the middle part of the building; and Mechanical supply air ventilation with heat recovery in sanitary facilities and staff room | Max 20 persons in a classroom, 400 persons in the building | Replacement air valves and powered replacement air hatches; Mechanical supply/air ventilation with heat recovery in sanitary facilities and staff room; and Potentially, the existing shafts need to be replaced with larger shafts | Inexpensive operating costs | A draught of air in a cold climate; Impurities enter indoor air because of nearby traffic; Lack of heat recovery (classrooms); Rooms that require mechanical exhaust ventilation, such as home economics, are challenging to place in the building with natural ventilation; A small number of pupils allowed; A need for a large number of shafts; even 2 sq. m per classroom; Traffic noise; and Relatively high installation costs, if shafts need to be replaced |
| Alternative 2 (A2) | Hybrid – fan assisted natural ventilation, heating and filtering the supply air, powered boost adjustment Centralised supply air Mechanical supply/exhaust ventilation with heat recovery in sanitary facilities and social rooms | Max 25 persons in a classroom, 500 persons in the building, air flow rate of 0.7 m3/s | Individual room shafts ∅ 400 mm for supply air and exhaust air; Electric filtering and radiators in the basement; Individual room shafts for supply air; and Mechanical supply/exhaust ventilation with heat recovery for exhaust air in sanitary facilities and staff room | The building will not maintain negative pressure inside; and Relatively large number of pupils | Challenges in placing air inlets due to a nearby road, a parking lot and a service road into the kitchen of the campus; Challenges in organising an exhaust air duct large enough into the basement; Almost a constant need to use mechanical ventilation; and Lack of heat recovery (classrooms) |
| Alternative 3 (A3) | Mechanical exhaust ventilation with supply air | 25/30 persons in a classroom, (S2/S3), 500/600 persons in the building, air flow of the ventilation unit 6 m3/s | Air supply units in the basement; Vertical shaft for air distribution; Exhaust air units into the attic; Exhaust air shafts Individual room adjustment for boost, occupancy sensors + on/off plates for boost; Sanitary facilities and staff room integrated with mechanical exhaust air units of classrooms; and Liquid heat recovery | Large number of pupils; and Savings in energy consumption because the air flow can be adjusted in each room separately | High operating costs but automatic adjustment is used as the base of the use; Challenges in keeping the pressure difference between indoor air and outdoor air constantly small to minimise air leakages through structures. A need for constant measurements and adjustments of pressure differences; Design requires high expertise; Challenges in placing air inlets; and About 1 sq m of space is needed for shafts in each classroom |
| Alternative 4 (A4) | Mechanical exhaust ventilation with supply air. Mechanical supply/exhaust ventilation with centralised exhaust ventilation through the roof of the third floor | 25/30 persons in a classroom, (S2/S3), 500/600 persons in the building, air flow of the ventilation unit 4.5 – 5 m3/s | Mechanical supply air units; Centralised exhaust ventilation from the roof of the third floor's corridor; Air ventilation and increased adjustment individually in rooms; Liquid heat recovery; Transfer air devices; and Sanitary facilities integrated into the same mechanical ventilation units | High modifiability: interior walls between classrooms and corridors can be removed without the need to modify ventilation equipment; Large number of pupils; and Energy savings by using individual room adjustments of air flow | Same challenges with the location of air inlets and maintenance of air pressure differences are connected to alternative 4 as alternative 3 has; Large transfer air devices are needed in the wall between classrooms and corridors; and Lower total air flow compared to alternative 3, the rating is based on the number of users, not square metres |
| Alternative | Operation | No. of users | Alteration work | Benefits | Downsides |
|---|---|---|---|---|---|
| Alternative 1 (A1) | Natural ventilation in the middle part of the building; and Mechanical supply air ventilation with heat recovery in sanitary facilities and staff room | Max 20 persons in a classroom, 400 persons in the building | Replacement air valves and powered replacement air hatches; Mechanical supply/air ventilation with heat recovery in sanitary facilities and staff room; and Potentially, the existing shafts need to be replaced with larger shafts | Inexpensive operating costs | A draught of air in a cold climate; Impurities enter indoor air because of nearby traffic; Lack of heat recovery (classrooms); Rooms that require mechanical exhaust ventilation, such as home economics, are challenging to place in the building with natural ventilation; A small number of pupils allowed; A need for a large number of shafts; even 2 sq. m per classroom; Traffic noise; and Relatively high installation costs, if shafts need to be replaced |
| Alternative 2 (A2) | Hybrid – fan assisted natural ventilation, heating and filtering the supply air, powered boost adjustment Centralised supply air Mechanical supply/exhaust ventilation with heat recovery in sanitary facilities and social rooms | Max 25 persons in a classroom, 500 persons in the building, air flow rate of 0.7 m3/s | Individual room shafts ∅ 400 mm for supply air and exhaust air; Electric filtering and radiators in the basement; Individual room shafts for supply air; and Mechanical supply/exhaust ventilation with heat recovery for exhaust air in sanitary facilities and staff room | The building will not maintain negative pressure inside; and Relatively large number of pupils | Challenges in placing air inlets due to a nearby road, a parking lot and a service road into the kitchen of the campus; Challenges in organising an exhaust air duct large enough into the basement; Almost a constant need to use mechanical ventilation; and Lack of heat recovery (classrooms) |
| Alternative 3 (A3) | Mechanical exhaust ventilation with supply air | 25/30 persons in a classroom, (S2/S3), 500/600 persons in the building, air flow of the ventilation unit 6 m3/s | Air supply units in the basement; Vertical shaft for air distribution; Exhaust air units into the attic; Exhaust air shafts Individual room adjustment for boost, occupancy sensors + on/off plates for boost; Sanitary facilities and staff room integrated with mechanical exhaust air units of classrooms; and Liquid heat recovery | Large number of pupils; and Savings in energy consumption because the air flow can be adjusted in each room separately | High operating costs but automatic adjustment is used as the base of the use; Challenges in keeping the pressure difference between indoor air and outdoor air constantly small to minimise air leakages through structures. A need for constant measurements and adjustments of pressure differences; Design requires high expertise; Challenges in placing air inlets; and About 1 sq m of space is needed for shafts in each classroom |
| Alternative 4 (A4) | Mechanical exhaust ventilation with supply air. Mechanical supply/exhaust ventilation with centralised exhaust ventilation through the roof of the third floor | 25/30 persons in a classroom, (S2/S3), 500/600 persons in the building, air flow of the ventilation unit 4.5 – 5 m3/s | Mechanical supply air units; Centralised exhaust ventilation from the roof of the third floor's corridor; Air ventilation and increased adjustment individually in rooms; Liquid heat recovery; Transfer air devices; and Sanitary facilities integrated into the same mechanical ventilation units | High modifiability: interior walls between classrooms and corridors can be removed without the need to modify ventilation equipment; Large number of pupils; and Energy savings by using individual room adjustments of air flow | Same challenges with the location of air inlets and maintenance of air pressure differences are connected to alternative 4 as alternative 3 has; Large transfer air devices are needed in the wall between classrooms and corridors; and Lower total air flow compared to alternative 3, the rating is based on the number of users, not square metres |
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