Archive for the ‘In the Field with Neil’ Category

In the Field with Neil: RESNET Chapter 8 Blower Door Numbers

Monday, August 26th, 2013

In July 2013 – Florida changed; some say for the better – others not so much so.  Never the less, change has occurred. For raters working in Florida, it means that we now have the option in how we perform blower door testing.  In the past, it was a requirement that for a registered rating – a multipoint test was needed.  Now we can do a single point. (For me personally, I like the multipoint test.  All the hard work is done; I only need to gather a few building pressures and corresponding flows.  I get more info about the building enclosure.  But this is for another blurb.)

So what does RESNET chapter 8 say…

802.1 ON-SITE INSPECTION PROTOCOL

There are three acceptable airtightness test procedures:

802.1.1 Single-point test: Measuring air leakage one time at a single pressure difference as described in section 802.5

802.1.2 Multi-point test: Measuring air leakage at multiple induced pressures differences as described in section 802.6

802.1.3 Repeated single-point test: The test is similar to the single point test, but the test is done multiple times for improved accuracy and estimating uncertainty as described in section 802.7

 

What are the highlights of each test process?

(Note that the house setup is identical no matter which test procedure you use – the difference is in the pressures and flows taken from the blower door.)

Let’s look at 802.5  Single-point test.

  1. Determine the baseline range – Fan sealed, record 5 different pressures (10 second average minimum) of house wrt outside. Find the difference between the highest and lowest values – This sets the Level of Accuracy.
  2. Determine the Pre-test baseline pressure – Average these 5 readings just taken may be used (or use baseline feature of meter – 10 second min).
  3. Determine the unadjusted building pressure and flow at 50 pascals – the building pressure to the nearest 0.1 pascal and the flow to the nearest cfm.  Also record inside/outside temperatures, fan/meter models/serial numbers, fan configuration and type of test (pressurize/depressurize).
  4. Perform calculations to determine corrected CFM50.  See the RESNET Standard section 802.5.9 for that process.  Or my suggestion is to download the FREE EnergyConservatory Tectite 4.0 (wifi) software.  You can select this test type and just input your numbers and out pops the result and you can save it for later viewing – like when the QA person comes around and asks to see your files…just saying.
  5. If you are using EnergyGauge USA (of course), enter the building pressure and corrected fan flow as shown. Click on Calculate/Post and it will do the calculations needed.

august

Now let’s look at 802.6  Multi-point test.

  1. Determine the Pre-test baseline pressure – Measure the house wrt outside using the 10 second average minimum (or use baseline feature of meter – 10 second min). Fan sealed during this step.
  2. Determine the unadjusted building pressures and flows– Take and record a minimum of 7 additional unadjusted building pressure and nominal fan flow measurements at target induced pressures which are approximately equally-spaced between 60 Pa (or the highest achievable induced building pressure) and 15 Pa. The building pressures to the nearest 0.1 pascal and the flows to the nearest cfm.  Also record inside/outside temperatures, fan/meter models/serial numbers, fan configuration and type of test (pressurize/depressurize).
  3. Determine the Post-test baseline pressure – Measure the house wrt outside using the 10 second average minimum (or use baseline feature of meter – 10 second min). Fan sealed during this step
  4. Complete steps #4 & #5 above.
  • Note: the current version of EnergyGauge USA doesn’t do the required adjustments to the as measured building pressures and flows – therefore download the FREE EnergyConservatory Tectite 4.0 (wifi) software; it will perform all the calculations needed.

Lastly look at 802.7  Repeated single-point test.

  1. Determine the Pre-test baseline pressure – Average these 5 readings just taken may be used (or use baseline feature of meter – 10 second min).
  2. Determine the unadjusted building pressure and flow at 50 pascals – the building pressure to the nearest 0.1 pascal and the flow to the nearest cfm.  Also record inside/outside temperatures, fan/meter models/serial numbers, fan configuration and type of test (pressurize/depressurize).
  3. Repeat steps #1 & #2 a minimum of 5 times.
  4. Calculate the Average Nominal CFM50 by summing the individual nominal CFM50 readings and dividing by the number of readings.
  5. Perform calculations to determine corrected CFM50.  See the RESNET Standard section 802.7.9 for that process or use the FREE EnergyConservatory Tectite 4.0 (wifi) software. If you are using EnergyGauge USA, enter the building pressure and corrected fan flow. Click on Calculate/Post and it will do the calculations needed.

In The Field With Neil: RESNET-Approved Airflow Measurement Techniques

Monday, June 17th, 2013

Chapter 8, section 804 of the RESNET Standard provides us with an onsite procedure for measuring the airflow of ventilation systems. These procedures treat the air flows into a grille and out of a register measured separately. There are 3 RESNET-approved test processes used to determine airflow: 1) powered flow hood, 2) air flow resistance and 3) timed bag inflation. Each method, as most things in life, has positives and negatives.

 

Powered Flow Hood

powerflow

The powered flow hood method is the most accurate, but also the most expensive. The powered flow hood differs from a conventional flow hood in that there is a fan which assists air movement through the flow hood to prevent a pressure differential at the register or grill created by the flow hood. The most common is the Energy Conservatory FlowBlaster® which works with your existing Duct Blaster Fan and DG-700 Pressure and Flow Gauge. The fan is powered by a combination fan speed controller and rechargeable Lithium-Ion battery. This method may be used on either exhaust or supply systems.

 

Air Flow Resistance

airflow

The air flow resistance method is probably the most common and can only be used on exhaust systems (air entering grill).  This method determines the air flow by measuring a pressure difference across a known hole size.  The air flow (in cfm) is equal to the hole size (in square inches) times 1.07 times the square root of the pressure difference (in pascals).  (Yes we are mixing units, but the 1.07 factor takes care of the conversions.)  This device will give the best results when the pressure difference is less than 8 pascals – largely because the exhaust fan speed will be reduced with greater pressures.  There is a commercially available “box” or flow meter again from the Energy Conservatory or you can easily create your own.  (If interested in creating your own – drop me a line and I will send you the directions.)

 

bag

Timed Bag Inflation

The timed bag inflation method is the least expensive of all.  It can only be used on supply systems.  As the name implies, a bag (typical a garbage bag) of known volume is inflated by the supply air.  The time required to fully inflate the bag is measured with a stopwatch.  This method takes a bit of practice to get repeatable results, but is rather simple to do.  As the standard indicates, bag volume and thickness play into the accuracy of the results – so a trial and error approach is needed.  Aim for a fill time of 2 to 20 seconds – the longer fill time will be easier to do, but may require a fairly large bag depending on the amount of airflow.  The airflow is easily calculated by multiplying the bag volume (in gallons) by 8 and dividing by the time (in seconds) required to fill it.  The Canada Mortgage and Housing Corporation has a nice write up on the method along with a table to convert to airflow.

 

These three procedures are the only RESNET-approved methods for measuring airflow in either whole house or spot ventilation systems.  (Well, there is one exception – if an ERV/HRV manufacturer has ports installed on their device for the purpose of measuring airflow; that may be used when following their directions.)

So go measure and have fun out there…

In The Field With Neil: Automatic Fan Control

Tuesday, May 7th, 2013

Most of us use either the Energy Conservatory DG-700 or Retrotec DM-2 digital micromanometers.  These meters have some great, yet under utilized features.  I would like to introduce you to one of the features – automatic fan control.  The Energy Conservatory refers to it as “cruise control” and Retrotec as “set pressure”.  In either case, it allows the digital pressure meter to control the fan speed or flow based on the pressure of “A” channel.

With the Automated Control you can…

  • quickly measure building airtightness using a “one-point” 50 Pa test.
  • quickly measure duct airtightness using a “one-point” 25 Pa total leakage test.
  • simultaneously control both the blower door and duct tester fans during a leakage to outside duct airtightness test. During this test, the meter will maintain a constant 25 Pa building pressure while the gauge connected to the duct tester fan maintains a constant 0 Pa pressure in the duct system.
  • maintain a constant building pressure while pressure pan testing, or locating and sealing building and duct system air leaks.
  • perform series leakage to quantify leakage rates between various zones within a building.  (Check out our class on Advanced Pressure Diagnostics…we will be using the cruise control a lot)

So this sounds great – what do you need in order to use the automated fan control feature?

  • An “automated fan compatible” gauge. Most are, but check that it has either “EC-cruise” or “Retrotec-set pressure” buttons on the front panel of your digital pressure gauge.
  • A blower door or duct tester fan speed controller with proper communication jack.
  • A cable to connect the meter to the fan.

That is it!  And you probably already have everything you need – especially if you recently purchased your equipment.  So next time you are out in the field – give it a try; I know you will ask yourself, ‘how did I ever get along without this?’.

For more information on automated blower door control:

In The Field With Neil: Digital Meter Calibration

Wednesday, March 27th, 2013

Spring is in the air – so what does that have to do with your manometer calibration?  Probably nothing, except Spring means new beginnings and we need to make sure that our equipment is up to the task ahead.

Question: Why do I need to have my manometer calibrated?

Simply answer – RESNET Standard dictates it and I quote from the standard:

802.9 Equipment Accuracy and Requirements
Blower door fans used for building air leakage testing shall measure airflow (after making any necessary air density corrections) with an accuracy of +/- 5%. Pressure gauges shall measure pressure differences with a resolution of 0.1 Pa and have an accuracy of +/- 1% of reading or 0.5Pa, whichever is greater.

Blower door and associated pressure testing instruments shall be tested annually for calibration by the HERS Rating Provider or Certified Rater. The provider shall use a standard for field testing of calibration provided by the equipment manufacturer. Magnehelic Gauges cannot be field tested and shall be recalibrated by the Blower Door manufacturer annually. Field check the fan and flow measuring systems for defects and maintain them according to manufacturers recommendations. The HERS Rating Provider or Certified Rater shall maintain a written log of the annual calibration check to verify all equipment accuracy for a period of three (3) years. These records shall be made available within 3 business days to the RESNET Quality Assurance Administrator upon request.

Therefore you have 3 options for compliance…

  1. Send your meter(s) to the manufacturer for calibration on a yearly basis.  This is the most expensive method, but has the advantage of having your meter calibrated and brought into factory specifications. (Click on the manufacturer link to go to their site).
    • The Energy Conservatory – TEC recommends that all of it’s digital pressure gauges be recalibrated once per year in order to maintain the instrument’s accuracy specifications of 1% of reading (or 0.15 Pa, whichever is greater). Calibration is performed at our facility in Minneapolis, MN. The cost to calibrate a digital pressure gauge is $75. This price includes return ground shipping within the continental 48 states and Canada (expedited or air shipments will cost more). Turn around time at our facility for calibration is typically 2-3 days following receipt of the instrument (assuming no repairs are necessary). We will provide a NIST traceable calibration certificate which includes “as found” as well as “current condition” pressure data.
    • Retrotec - Our recommendation for manufacturer calibration is: – Every two years for DM-2 pressure gauges – Every five years for the entire flow measurement system.  You will need to send in or call to get a price quote.

     

  2. Send or bring in your meter to us at FSEC.  We will do a field calibration check on your meter(s).  We do not modify, adjust or certify the meter – only verify whether it is within factory specifications.  If your meter is not in spec, we will let you know and it needs to be sent out for repair/factory calibration.  Our cost – FREE to our raters.
    • Make an appointment with Jimmy Williams (jwilliams@fsec.ucf.edu) if you are bringing them by (it takes about 30 minutes to do the check)
    • Send them in to:
      Jimmy Williams, Florida Solar Energy Center, 1679 Clearlake Rd, Cocoa, FL  32922
      • You prepay for the shipping both directions.
      • We are not responsible for any loss or damage done through shipping.

     

  3. Perform a field calibration per the manufacturer as done by a certified RESNET Rater (Class 1 rater in Florida).

     

Now, one more thing – if FSEC is your rating provider, we need a copy of the field calibration for each meter you use.

Send us a copy (pdf format to: Jimmy Williams (jwilliams@fsec.ucf.edu) or by mail  to Jimmy Williams, Florida Solar Energy Center, 1679 Clearlake Rd, Cocoa, FL  32922).  The nice thing about option #2 is that not only is the calibration check free – but all the paperwork we need is done.

In The Field With Neil: Depressurize or Pressurize Airtightness Test

Friday, March 1st, 2013

Question: Should the blower door test be performed in a pressurized or depressurized mode?

blowerDoortest

The blower door test follows ASTM standard E779 (Standard Test Method for Determining Air Leakage Rate by Fan Pressurization), which states that this test method consists of mechanical pressurization or de-pressurization of a building and measurements of the resulting airflow rates at given indoor-outdoor static pressure differences.  From the relationship between the airflow rates and pressure differences, the air leakage characteristics of a building envelope are determined.  It is intended to quantify the air tightness of a building envelope and does not measure air change rate or air leakage.

So the answer is… either method is acceptable.

In general, we tend to depressurize buildings as it prevents a jet of air from being blown into the house during the test process.  However, under certain conditions it is necessary to conduct a blower door test by pressurizing the building.  For example, pressurization testing may be used to avoid the possibility of pulling known pollutants into the building during the test procedure (e.g. mold from wall cavities or crawlspaces). The pressurization test also requires an additional outside reference hose connected to the meter.

Remember it is fan sensor with reference to fan sensor location.  Therefore if we are using a DG-700 meter, the fan sensor would be installed on the B-side input tap and the outside reference connected to the B-side reference tap.

Tip from Neil:
When reporting your results – we assume that a depressurization
test was done.  If you tested otherwise, be sure to document it.

In comparing the results of a pressurization test to that of a depressurization test, in general the depressurization test will yield a slightly tighter structure.  The reason is quite simple.  A depressurization test tends to pull dampers closed (i.e. bath fans, kitchen fans and dryer vents), whereas the pressurization test will tend to force them open.