Building & Construction

Condensation Management

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Course Summary

1) REFRESHER ON CONDENSATION MANAGEMENT PRINCIPLES

  • (This is a review of the core hygrothermal principles which refreshes attendees and segues into the subsequent presentations)
  • Why condensation is more of an issue in high performance buildings (7 star and above).
  • Air tightness problem – less exchange of air mass in well-built buildings and how this affects internal humidity and IAQ/health
  • Vapour load problem – as houses are heated more the ability to hold moisture and desorb moisture from porous materials increases
  • Dew point shift – as buildings are better insulated moisture in walls will condense further inside the built fabric
  • All of these above points will touch on the following presentations to make them more relevant

2) AIR TIGHTNESS AND ITS MEASUREMENT

  • What a blower door test is and what it measures
  • Current requirements for air tightness in NCC – are they effective?
  • What ACH@50 is assumed in EE calcs/NaTHERS
  • What ventilation requirements are required in NCC (vol 1 and vol 2)
  • Typical air tightness of modern buildings – high risk constructions (e.g. class 2)
  • What ACH@50 relates to as ACHnatural
  • The “valley of death” and air tightness and how to avoid it
  • Air tightness and air quality – health
  • Air tightness and internal humidity – mould etc
  • Make up air, balanced air exchange and a plenum
  • Natural ventilation vs MHRV

3a) BUILDING WRAPS EXTERNAL AND INTERNAL

  • A brief overview of vapour permeable membranes
  • Microscopic detail of membrane technology (microporous vs monolithic vs perforated (!!!) )
  • Requirements of WRBs and AS4200/NCC (Table 4, temp ratings, water barriers etc)
  • Is a perforated foil suitable and why/why not?
  • How important is air leakiness inside and outside of the WRB (e.g. do non-passive houses benefit from full taping of the WRB from roof to walls)
  • Other ways to deal with WRBs (e.g. RAB board)
  • Leakiness of the rainscreen – drainage, ventilation, solar penetration, BAL
  • Fire rating in multirise (intumescent seals, Approved Document (UK)*
  • AVCL/internal vapour and air control layers
  • What they are specifically intended to do
  • Brief reference to international history (Canadian building manual 2000, BS5250)
  • Sealing of the system

3b) OTHER METHODOLOGIES TO DEAL WITH MOISTURE AND CONDENSATION (Andy Russell’s “2 of the 4” principles)

(Most of the information for resi/low rise builders deals with vapour permeablilty of WRB, but deals little with other valid methods of addressing the problem. This could include information on other façade, roof, deck designs like those in the DCTech library- rockwool in rainscreen façade systems, outsulation generally, high density extruded polystyrene under waterproof decking systems. This could feed into a practical session on how these systems are installed. There is also scope for installation of drainage batten and associated products (Vent Systems) as both minimal compliance and high performance solutions.)

4) LATEST UPDATE ON RESEARCH

  • International history of hygrothermal modelling
  • What is a mould growth index and why is it used
  • How much ACH affects EE (are we making buildings too tight)
  • How important is ACH for mould and IAQ
  • Is 7 star a “tipping point” for mould in buildings
  • Modelling graphs showing cycling of moisture/VTT over many years
  • How essential is mechanical ventilation in 7 star buildings
  • How modelling of DtS meets verification method in NCC 2022
  • Is passive house the answer to everything and what are most important principles for non PH builds
  • Window quality and condensation (alum frames will always condense)*
  • BAL designs*
  • Design considerations for above matters
  • Services within insulated spaces (like mHRV)
  • Heat and AQ in ceilings and subfloor spaces
  • Balanced air and makeup air
  • Mould risk in different wall lay ups and orientations

5) PRACTICAL SESSIONS

  • Installing internal and external wraps and systems
  • Design considerations and practical session for installing mHRV systems
  • Installation of various wall/roof systems from DCTech library, rockwool rainscreen façade systems etc with specific inclusion of decks over habitable rooms.

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