Builder s Technical Sessions. Attic Ventilation. Presented by: Rob Kaethler. Presented in Partnership with: Insert your logo here

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Gavin Dean
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1 Builder s Technical Sessions Attic Ventilation Presented by: Rob Kaethler Presented in Partnership with: Insert your logo here

2 Residential Ventilation Agenda Principles of Ventilation Types of Ventilation Building Code Vented and Un-Vented Attics Balanced Ventilations Cold Weather roofing New products and solutions Trends

3 Poor Ventilation

4 Insufficient Ventilation

5 Adequate Ventilation

6 Roofing Manufactures Require Ventilation

7 Vent Requirements 1) Except as provided in sentence (2), the unobstructed vent area shall be not less than 1/300 of the insulated ceiling area 2) Where the roof slope is less then 1 in 6 or in roofs that are constructed with roof joists, the unobstructed vent area shall be not less than 1/150 of the insulated ceiling area 3) required vents may be roof type, eave type, gable-end type or any combination thereof, and shall be distributed a) uniformly on opposite sides of the building b) with not less than 25% of the required openings located at the top of the space, and c) with not less than 25% of the required openings located at the bottom of the space 4) except where each joist is separately vented, roof joists spaces shall be interconnected by installing purlins not less than 38mm by 38mm on the top of the roof joists 5) vents shall comply with CAN3-A93-M, Natural Airflow Ventilators for Buildings

8 Highlights of Building Code 1 in 300 rule for normal attics 1 in 150 rule for rafter attics Uniformly on opposite sides of the roof Minimum 25% at or near ridge Minimum 25% at or near the bottom Meets CSA

9 Three Strategies for Controlling Moisture in Roof Assemblies: Controlling moisture entry. Controlling moisture accumulation. Removing moisture that does accumulate by drying.

10 Un-Vented Roofs Un-vented roofs operate on the principle that moisture can be controlled from entering the roof assembly The building must have a tight building envelope The different parts of a building must be properly pressurized

11 Un-Vented Roofs Building code doesn t totally allow for it Shingle manufactures may not allow for it There is no margin of error Shingle longevity may be be reduced

12 Vented Roofs Remove moisture from roof cavities Control ice damming Enhance roofing material life span Increase occupant comfort

13 Vented Roof Assumptions The building envelope is tight The roof assembly has enough insulation Inlet and outlet areas are distributed evenly The outside air is able to absorb moisture

14 Cold Weather Roofing Keys Minimize the amount of moisture attic ventilation must deal with Use a good vapour retarder Reduce air leaks through the ceiling Educate home owners about indoor humidity levels during cold weather

15 The Stack Affect Attic air heated by contact with a hot roof on a warm day tends to rise. This is natural convection, which pulls cooler air from the soffit up towards the ridge. Natural convection, with a balanced system of soffit and vents at or near the ridge is the most effective means of venting the roof. The steeper the roof pitch the better the stack affect works in particularly cold weather

16 NFA (Net Free Air) or Airflow or CFM NFA is a static measurement; Airflow is a dynamic measurement. Cubic feet per minute

17 Balanced Ventilation Means for every inch of air exhausted, it must be balanced by providing the same or greater amount of air intake at the eaves or soffits. Why is balance so important

18 Balanced Ventilation

19 Cold Weather Venting

20 Why Vent an Attic In Cold Weather Reduce ice dams and icicle ups Remove moist air from the attic Occupant comfort

21 Ice Ups and The Icing Envelope Snow melts on the roof The melt water refreezes 22 F or -5.6 C is the magic number

22 Why We Vent in Cold Weather Snow on the roof begins to melt anytime the attic temperatures reaches 30 F(-1.1C), but only refreeze when the outdoor temperature is below 22 F (-5.6C) This is called the icing envelope Ice dams could be avoided if attic ventilation could maintain the attic at 30 F or lower when the outdoor temperature was 22 F or lower Army Core of Engineers the Icing Envelope

23 Why we Vent in Cold Weather Ice Damming

24 Cold Weather Roofing Keys The system approach Insulation Vapour Retarder Ventilation

25 Cold Weather Roofing Keys Insulation A properly insulated home keeps as much of the heat in the house as possible Keeps the attic as cold as possible Saves money

26 Cold Weather Roofing Keys Ventilation Balance the ventilation What is your air intake? What is your air exhaust What solution are you using? Why Certifications It is tougher to keep snow out of an attic then rain

27 Types of Vent Solutions

28 Potential Vent Options Front and back soffit venting Gable end vents Traditional plastic or metal pot vents Ridge vents Off peak vents Power ventilators Wind driven Ventilators

29 Front and Back Soffit Venting Dropped Gabel Truss Slots for Ventilation

30 Front and Back Soffit Venting

31 Products and Solutions Air intake vents installed low on the roof

32 Trends Solutions to specific application Low or no maintenance Curb appeal Longevity of our roofs

33 New Products and Solutions Off-peak air intake vents Air Intake Vent

34 Vents for Special Applications Roof meets a wall

35 New products and solutions Vents For Hip

36 New products and solutions Vents for specialty applications Flexible Vents

37 Powered Ventilation

38 Drawbacks of Powered and Mechanical Ventilators If the fan is turned off how much NFA are you getting? If it is a mechanical device and it does not function correctly how much NFA are you getting? If the air intake doesn t match the air exhaust where does it get the additional needed air?

39 Certifications and Standards Is it a standard that requires certification or compliance? Does the vent have to be modified to meet the standard? Is this important?

40 Miami Dade County Wind driven rain test 8.8-inches of water at 110 miles per hour Independent NFA Verification Static Pressure Uplift Independent NFA Verification Wind driven snow tests Dust exposure test TDI ICC

41 UL and ULC Fire Testing Code compliance testing CAN3-A93-M CSA

42 Conclusion Reduce the moisture load to the attic from the house Make sure you have a balanced system Air intake is critical Vent for all the weather conditions and all seasons

43 Questions?

Attic Condensation. Presented by: Joan Maisonneuve Technical Services

Attic Condensation. Presented by: Joan Maisonneuve Technical Services Attic Condensation Presented by: Joan Maisonneuve Technical Services Scope of the Presentation How does moisture get into the attic? Blowing snow Moisture from the outdoor air Moisture from side-vents