Design for Airtightness and Moisture Control in New Zealand housing

Transcription

1 Design for Airtightness and Moisture Control in housing paola leardini the university of auckland [school of architecture & planning] thomas van raamsdonk pro clima nz limited

2 current issues Indoor Air Quality Recommendation Temperature < 16 o C 18 o C - 24 o C Relative Humidity > 65% 40% - 60%

3 current retrofitting practice Existing Housing Stock insulation ceiling underfloor double glazing heating / cooling heat pumps wood burner gas fire

4 current retrofitting practice Existing Housing Stock insulation ventilation enables Airtightness moisture control enables heating / cooling What MEASURABLE OUTCOMES do we need to look at to improve IAQ?

5 current retrofitting practice Existing Housing Stock OUTCOMES insulation was associated with a small increase in bedroom temperatures during the winter (0.5 C) and decreased relative humidity ( 2.3%) Philippa Howden-Chapman [2007] Effect of insulating existing houses on health inequality: cluster randomised study in the community insulation ceiling underfloor double glazing heating / cooling heat pumps wood burner gas fire

6 what is Airtightness? Blower Door Test protecting against uncontrolled air movement through the building envelope

7 requirements for Airtightness Building Code Clause H1

8 measuring Airtightness Blower Door Test n50 = volume of air transported outwards by the Blower Door net volume of air of the building

9 measuring Airtightness Blower Door Test

10 measuring Airtightness Blower Door Test

11 measuring Airtightness Blower Door Test

12 measuring Airtightness Blower Door Test

13 measuring Airtightness Existing Housing Stock TYPE AIRTIGHTNES S AC/H 50 PA BUILDING DESCRIPTION AIRTIGHT 5 ac/h post 1960 houses with a simple rectangular single story floor plan of less than 120 m 2 and airtight joinery (windows with airtight seals) AVERAGE 10 ac/h post 1960 houses of larger simple designs with airtight joinery LEAKY 15 ac/h post 1960 houses of more complex building shapes and with unsealed windows DRAUGHTY 20 ac/h All pre 1960 s houses with strip flooring and timber windows Classifications of residential building airtightness Bassett, M.R N e w Z e a l a n d S u s t a i n a b l e B u i l d i n g C o n f e r e n c e [ S B 1 0 N Z ] M a y Te P a p a / W e l l i n g t o n

14 Europe measuring Airtightness Standards Germany [EnEV 2009] n ACH buildings without ventilation equipment n for ACH buildings with ventilation equipment n for ACH Passive House requirement

15 Europe measuring Airtightness Passive House Standard Passive House Standard n for ACH space heating demand doubles!

16 Europe importance of Airtightness Insulation Performance experiment conditions: 1m 14 cm 1m without gap: R-Value = 3.30 W/m 2 K with 1 mm gap: R-Value = 0.70 W/m 2 K inside temperature +20 C outside temperature -10 C Pressure difference 20 Pa = wind force 2-3 Measurement: Institute of building physics, Stuttgart Source: DBZ 12/89, page 1639ff performance down by factor 4.8!

17 Europe importance of Airtightness Insulation Performance experiment conditions: 1m without gap: with 1 mm gap: 14 cm 1m 0.5 g water / m2x24h 800 g water / m2x24h inside temperature +20 C outside temperature -10 C Pressure difference 20 Pa = wind force 2-3 Measurement: Institute of building physics, Stuttgart Source: DBZ 12/89, page 1639ff FACTOR 1,600!

18 mvtr-value [MNs/g] N e w Z e a l a n d S u s t a i n a b l e B u i l d i n g C o n f e r e n c e [ S B 1 0 N Z ] M a y Te P a p a / W e l l i n g t o n Europe importance of Airtightness Insulation Performance mvtr-mean value at varying humidity levels vapour barrier winter summer average air humidity [%] e.g. PE sheet: mvtr = 250 MNs/g no possibility for constructions to dry out when unexpected moisture occurs

19 importance of Airtightness Insulation Performance moisture movement vapour barrier e.g. PE sheet: mvtr = 250 MNs/g summer no possibility for constructions to dry out when unexpected moisture occurs

20 mvtr-value [MNs/g] N e w Z e a l a n d S u s t a i n a b l e B u i l d i n g C o n f e r e n c e [ S B 1 0 N Z ] M a y Te P a p a / W e l l i n g t o n importance of Airtightness Insulation Performance variable MVTR winter summer relative humidity [%]

21 importance of Airtightness Insulation Performance ca. 80 % ca. 70 % variable MVTR direction of the diffusion direction of the diffusion ca. 30 % ca. 90 % ca. 50 % ca. 70 % average environmental humidity of the vapour barrier average environmental humidity of the vapour barrier 40 % 80 % winter summer

22 mvtr-value [MNs/g] N e w Z e a l a n d S u s t a i n a b l e B u i l d i n g C o n f e r e n c e [ S B 1 0 N Z ] M a y Te P a p a / W e l l i n g t o n importance of Airtightness Insulation Performance variable MVTR variable MVTR winter summer relative humidity [%]

23 retrofitting Existing Housing Stock 1. early colonial timber cottage 2. developed colonial cottage 3. victorian villa 4. victorian cottage 5. californian bungalow 6. english cottage style house 7. art deco 8. labour state house 9. star flat block

24 retrofitting: case study Labour State House ground plan

25 retrofitting: case study Labour State House

26 retrofitting Calculation Methods WUFI computer-assisted [dynamic] simulation program for heat and humidity transport (Fraunhofer, Germany) - real climatic data - inside and outside temperature - inside and outside humidity - light absorption - moisture storage capability - capillary action [data of one reference year at intervals of 1 hour]

27 retrofitting: case study Labour State House RH = 100% condensation N e w Z e a l a n d S u s t a i n a b l e B u i l d i n g C o n f e r e n c e [ S B 1 0 N Z ] M a y Te P a p a / W e l l i n g t o n

28 retrofitting: case study Labour State House Vapour check [variable transmission resistance] MNs/g 53 MNs/g RH < 100% during the calculation period (3 years) N e w Z e a l a n d S u s t a i n a b l e B u i l d i n g C o n f e r e n c e [ S B 1 0 N Z ] M a y Te P a p a / W e l l i n g t o n

29 Conclusion retrofitting + new construction Future A sound building is like a sturdy tripod, standing on three legs: ventilation adequate insulation and effective air-tightness It needs all three legs to stand. If we focus on just insulation with heating and cooling we create more problems than we solve and the tripod can t stand. Verification through Blower Door tests and WUFI calculations are needed to ensure we are indeed creating energy efficient, durable, healthy buildings

30 thank you SB10 N e w Z e a l a n d S u s t a i n a b l e B u i l d i n g C o n f e r e n c e [ S B 1 0 N Z ] M a y Te P a p a / W e l l i n g t o n

31 Conclusion retrofitting + new construction Future A sound building is like a sturdy tripod, standing on three legs ventilation, adequate insulation and effective airtightness. It needs all three legs to stand. If we focus on just insulation with heating and cooling we create more problems than we solve and the tripod can t stand. Verification through Blower Door tests and WUFI calculations are needed to ensure we are indeed creating an energy efficient, durable and healthy building.