Put the V back in HVAC

Transcription

1 Put the V back in HVAC

2 V is for Ventilation A system or means of providing fresh air. Webster New Collegiate Dictionary

3 Benjamin Franklin so unwholesome as air in a closed room that has been often breathed and not changed.

4 The Saskatchewan Conservation House was built in 1977 was one of the first energy conservation demo houses in North America. Over 30,000 people toured the twostorey structure; cubicle in shape, airtight and equipped with a heat recycling system.

5 Design and construction of low cost ventilation air heat exchangers DISCUSSION AND CONCLUSIONS The design of a low cost ventilation air heat exchanger has been presented. Such a heat exchanger could be used to recover most of the thermal energy from ventilation air which must be brought into buildings by fans. The experimental results indicate that such a heat exchanger should be operated so that gravitational forces assist the flow and hence the heat transfer then the flow rates are low and the flow is laminar. The method of optimizing costs over a specified period of time presented indicates that the use of low cost materials such as plastics permits the designer to use very high heat exchanger effectiveness values. In very cold climatic conditions frosting occurs therefore periodic defrosting must be provided for in the design.

6 A little history HRV / ERV Performance Testing 1 st North American residential HRVs developed in late Inconsistent performance, especially in cold weather cores frosting up Canadian R-2000 Housing Program sponsored development of a performance test standard and an CSA C439 - Standard Methods of Test for Rating the Performance of Heat Recovery Ventilators 6

7 HRV / ERV Performance Testing CSA C439 Air flow performance at different duct pressures Energy performance at different temperatures & air flows: At 32 F (O C) & others selected by manufacturer Typically -13 F (-25 C), 95 F (35 C) - Fan power consumption Cross leakage testing 7

8 Example of HRV / ERV Ratings

9 HRV / ERV Performance Testing Testing & reporting of results is now administered by HVI Home Ventilating Institute Look for this label Testing & labeling is voluntary Currently no European manufacturers have successfully completed cold weather testing Cold weather (-13 F) test is very rigorous 9

10 HRV / ERV Performance Testing Home Ventilating Institute 1. Tests and labels product 2. Verifies performance (air flow and sound / sone) 3. Provides listing of products online: 4. Offers challenge program so manufacturers can validate performance of competitors 10

11 HRV / ERV Performance Testing 1. Always choose labeled product Check the HVI website 2. Choose products that have been tested to temperatures at least as low as your local design temperature down to -13 F 3. Choose products that meet your air flow needs at performance 4. Then look for highest Sensible Recovery Efficiency it is the best indicator of overall energy performance 11

12 Air Flow Ratings Specify Rated Equipment work installed

13 Efficiency Ratings Sensible recovery efficiency is the best overall measure of energy performance in heating months It includes fan energy, core performance, defrost, cross contamination Apparent sensible is just the temperature change across the core Total recovery months

14 Ventilation... Methods, amounts & strategies

15 IAQ Strategies 1. Eliminate 2. Seal 3. Ventilate 4. Filter

16 Why Ventilate? To control humidity To control pollutants People - respiration (primarily CO2), perspiration, cooking, hobbies, parties, pets, cleaners Buildings materials, furnishing, combustion gases, radon, water vapor Outdoor air is always better than indoor air

17 VENTILATION IS A VERY POWERFUL DEHUMIDIFIER IN WINTER Examples When outdoor air is 16 F and 100% RH, 60 CFM of continuous ventilation can remove approximately 20 quarts / day from indoor air. When outdoor air is 32 F and 100% RH, 60 CFM of continuous ventilation can remove approximately 12 quarts / day from indoor air.

18 Goals of Mechanical Ventilation Stale air out, fresh air in To control moisture To reduce pollutants levels To filter incoming air Ventilate for people (continuous) Capacity for supplementary ventilation when needed (intermittent) Distributed, quiet, comfortable, controlled

19 New California study 75% of houses without mechanical ventilation had air change rates below code All the homes exceeded formaldehyde guidelines These results suggest that consideration should be given to installing mechanical ventilation systems in new single-family residences to provide a dependable and continuous supply of outdoor air so that indoor sources of formaldehyde are reduced. Window usage, ventilation, and formaldehyde concentrations in new Calif. homes

20 Builders need to commit to ventilation, that means: A good HRV / ERV Properly installed and balanced (proper hoods, ductwork and controls) A system that is operated and regularly maintained (education) 20

21 How Much Ventilation? ASHRAE: Standard 62-2 So much per person (bedrooms) Additional ventilation based on Floor Area Other factors: Moisture generation rates, source strength of pollutant, occupant sensitivity Number of occupants

22 Whole house ventilation ASHRAE 62.2 Every home needs the capacity for mechanical ventilation to manage moisture and dilute pollutants over and above air leakage and opening windows There are exceptions are for warmer climates where windows are expected to be open for extended periods 7.5 cfm per bedroom +1 extra + 1 cfm / 100ft2 More people - more capacity

23 Ventilation Sizing The minimum ventilation needed to control moisture, odors and other pollutants Ventilation Capacity 4 bedrooms + 1 or 5 x 7.5 cfm cfm = 63.9 cfm

24 Whole-House Ventilation Method # 2 This is the minimum rate more ventilation may be needed in some cases (additional capacity) Table from 62.2 Floor Area # of Bedrooms < 1500 Sq. ft. 30 cfm 45 cfm 60 cfm

25 Balanced Ventilation HRVs / ERVs can be independently ducted or integrated into forced air system Choose systems that are rated by the Home Ventilating Institute Select units with the right air flow Appropriate for your climate zone. Graphics Courtesy of Building Science Corp.

26

27 HRV / ERV the LUNGS of the Home Recover as much as 70% - 80% of the energy from the exhaust air stream Stale air to outside Recovery core Fresh air to the home Fresh air from outside Stale air from the home

28 Keep in mind, builders need ventilation solutions Solutions that work in the home, not in the box - installed.

29 Heat Recovery Ventilators (H / ERVs) Two ducts to outside Exhaust air out Two fans in a box: One exhausting air out. One bringing fresh air in. Heat Recovery Core Fresh air in Air in = Air out Recovers energy from exhaust and transfers it to the fresh incoming air.

30 Locating the unit to: Minimize noise/vibration - avoid the quiet rooms Keep insulated duct runs as short as possible. Provide access for maintenance. Be near a power outlet Be near drainage, near laundry or floor drain. 30

31 Hood Location The fresh air hood: height, whichever is greater. Consider using a snorkel in high snow locations. just about anything: gas meter, dryer vent, range outlet, water heater / furnace vent. Away from driveways Easy access for cleaning, not under decks 31

32 Outside hoods This style of hood allows excellent airflow. Exhaust air out Fresh air in Avoid this style of hood, it is very restrictive on airflow. Tandem Hood: Some specialized hoods from exhaust. 32

33 Installing insulated duct Keep runs short and straight. Support it well. Both the fresh-air duct from outside and the exhaust duct to outside need to be insulated. Seal both the inside liner and the outer vapor barrier really well against air leakage. 33

34 Duct rules: Keep it short and straight. Keep it smooth (rigid not flex). Tape and screw all joints. Go with the flow (direction of air flow) 34

35 H / ERV controls Manufacturers offer a variety of controls: A main control that is centrally located, often near the thermostat - OFF / LOW / HIGH speed operation Often includes a dehumidistat to turn the HRV to high speed if the humidity rises above the set point. Some main controls have an option, ventilate for 20 minutes on the hour (good for extended cold weather or holidays) 35

36 H / ERV controls Timers for bathrooms - turns the unit to high speed for a specified time, usually 20 minutes (typically eliminates the need for a bath fan) Get the controls that go with the unit (same manufacturer) Run low voltage wires from the HRV to the controls - telephone or thermostat wire is typical, check the manual for details.

37 Distribution options: Exhaust always draw stale air from kitchen and bathrooms Supply - if forced air with ECM motor, supply fresh air to the return duct - if radiant or baseboard, duct fresh to all bedrooms and main living areas Note: Using the furnace ducts for both exhaust and supply distribution

38 Ducting Rough-in of high wall exhaust or supply grill. Rough-in for kitchen grease filter grill.

39 The grilles: Kitchen exhaust grills - high wall, grease filter Bathroom exhaust grills - high wall Fresh air grills - high wall in bedrooms and main living areas

40 Note: for slab on grade, use ceiling drops in the hall to run ductwork

41 Why HRVs Fail Incorrectly installed System not balanced Poor ductwork, poor hoods Ductwork and HRV installed outside the home Unit is turned off (noise, comfort) Lack of maintenance operate and maintain the unit Wrong unit Too large / too small for the job 41

42 Balancing the HRV (using flow collars) 42

43 Balancing procedure with airflow stations Balance airflows within +/-10% for proper operation 43

44 Other balancing procedures Individual manufacturers may have different balancing methods : Some use pressure taps built into the door. Some use a bayonet style probe Some use fan speed adjustments rather than dampers.

45 Signs of improper balancing Excessive cold air from fresh-air duct. Frost on fresh-air pipe to the furnace or house. Frozen door locks. High electrical bills. Backdrafting of chimneys. Poor moisture removal. HRV turns itself off. 45

46 HRV Maintenance Every 3-4 months Check and clean filters Once each fall Clean HRV core Check and clean intake vents, grilles, hoods Check operation of dampers / controls

47 - Heat Recovery Ventilation Allows transfer of sensible heat temperature difference Energy Recovery Ventilation Allows both sensible and latent transfer Moisture transfer Reduces cooling loads in humid climates Avoids over-drying in winter Poly or Aluminum Core Permeable Core or Wheel

48 Depressurization testing A pressure gauge is used to measure the pressure between outside and inside. Chimney flues are blocked for the test Turn on exhaust fans one at a time. If pressure is below 5 Pa is required. If pressure is greater than 5 Pa, provide make-up air. 48

49 Fresh air distribution / mixing is essential for good IAQ with all systems!

50 The opportunity America needs healthy, energy efficient houses Healthy homes need good ventilation You are well placed to take advantage of the opportunities There is good work to be done good money to be made Go get it!

51 Changing the Course of Housing

52 We will change for the better or be changed for the worse. Wendell Berry 52 Heating Systems

53 Thank You!