Airtightness: When it s not as airtight as it s cracked up to be!

Transcription

1 Airtightness: When it s not as airtight as it s cracked up to be! 11 th March 2015 Niall Crosson: Technical Engineer MEngSc, BTech, MIEI, CEPHC

2 Presentation Summary: -Introduction - Airtightness Recap - Unexpected air leakage by materials - Unexpected air leakage by design - What else would you expect! - Summary - Questions

3 Introduction to Ecological Building Systems Demonstration and Training Centre: Athboy, Co Meath

4 Introduction to Ecological Building Systems Low Energy/Passivhaus new and existing buildings

5 Why Airtightness Infiltration and Ventilation Air Infiltration/Draughts and exfiltration The uncontrolled entry or exit of outdoor or indoor air from the habitable space Ventilation The controlled/designed replacement of stale indoor air with fresh outdoor air Airtightness The elimination of uncontrolled air infiltration BUILD TIGHT AND VENTILATE RIGHT!

6 Why Airtightness? REF: TARGET ZERO GROUP

7 Delivering Airtightness: Plan Ahead Clearly define air barrier layer and detail airtightness solutions Air barrier line Air leakage path

8 The principle of insulation air movement = heat transport only inclusions of air that are protected against air movement insulate!

9 The principle of thermal insulation: Airtightness

10 The principle of thermal insulation: Windtightness

11 Typical construction situation Consequences of defective air-tightness Airflow (Convection) Luftströmung (Konvektion) 1. Heat loss 2. Building damage due to moisture 3. Deficient heat protection in summer 4. Deficient sound proofing

12 Heat losses due to Convection 1m 1m Without gap: With 1 mm gap : U-Value = 14 cm U-Value = 0,3 W/m 2 K 1,44 W/m 2 K Performance reduced by factor 4,8 Experiment set-up Construction of insulating material Gap in the vapour Check (air-tightening). Frame conditions: 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

13 Comparison diffusion/convection Experiment set-up constr. of insulating material 1m 14 cm 1m Without gap: 0,5 g water/m 2 x24h With 1 mm gap: 800 g water/m²x24h Performance reduced by factor 1600 Inside vapour seal s d = 30 m (mvtr = 150 MNs/g]) Gap in the vapour Check (air-tightening) Frame conditions: 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

14 Plan Head! REF:

15 Make sure blocks are continuously plastered! Ref: Paul Jennings

16 Isn t OSB Airtight That s what we thought!

17 THEN THIS HAPPENED!

18 Test on Passivhaus 1 in Dublin: 2010 N50 = 0.9 with taped OSB N50 = 0.55 with membrane applied over OSB

19 Test on Passivhaus 2 in Dublin: 2011 N50 = 1.2 with taped OSB

20 OSB was lined and with air barrier membrane and N achieved.

21 International research on air permeablity of OSB

22 Results from Passivhaus Institute Paper IN sample case, for Passivhaus construction, allow for additional leakage of 20% -40% when using 18mm OSB as the airtightness layer!!

23 Results for Catholic Universtiy Leuven Paper IS OSB AIRTIGHT? Study University KU Leuven 8 brands OSB from 6 EU countries CONCLUSION: OSB as airtight layer in passive houses is questionable!

24 One Solution is to factory apply a Airtightness and Vapour Control Layer

25 Unforseen air leakage at the design stage

26 Vapourblock : USP s - integrated industrial vapour control layer during production of a wood based panel - guarantees constant μ value over the whole surface of the board instead of average μ value - no need to install separate membrane foil : faster installation, no risks of damage - guarantees at the same time consistently high levels of air tightness - high racking strength (structural board suitable for use in humid conditions P5 EN 312) - can also be applied without Vapourblock coating as external diffusion open racking board - available in moisture resistant, low formaldehyde and fire retardant version - offers all-in-one solution - large stock thicknesses / sizes available - large board dimensions available on request up to 2620x6350mm - assists in the design of a healthy living environment and durable construction - PEFC

27 Sometimes Windows Can leak even the best ones Leakage identified associated with windows despite them being PHI certified Temporary sealed over openings with polythene Depressurised with blower door plastic bulges inwards Comparing before & after readings gives effective leakage area of windows REF: P Jennings

28 Ensure everyone on site understands airtightness!

29 Ensure everyone on site understands airtightness!

30 Airtight Solution: Airtight Attic Hatch

31 Appropriate glues and tapes - resistance against moisture and high humidity

32 High quality tapes inner strength of the glue

33 High quality tapes - resistance against humidity Glue strength after 24h under water stress

34 Training and correct application of airtight materials

35 Experience is priceless

36 Training & sharing experiences & information

37 Airtightness Summary Airtightness: 1. Determines the effectiveness of the insulation Layer 2. Airtightness must be planned at design stage to deliver airtight buildings 3. A lack of foresight at design and construction stage leads to increased costs, and poorer results 4. Materials fit for purpose must be used to deliver durable airtightness solutions 5. Coordination and planning on site central to delivering positive results 6. Intermediate airtightness quality airtightness tests a must for optimum performance and increasing awareness on site 7. To achieve this the airtightness layers must be meticulously sealed to one another and to proximal structural components 8. Knowledge & training from design to site critical

38 Thanks! Final Questions?