Posts Tagged ‘fans’

Angry Air!

June 7, 2017

John Tooley said, “Air is like crooked rivers, crooked people, teenagers, and cheap labor.  It always seeks the path of least resistance.”  He didn’t say that Angry air is Noisy air.   Air doesn’t like being forced through corrugated, flexible ducting, pushed around corners, and made to force open dampers.  It resists being made to perform in a way that it doesn’t want to.  It takes more and more force as the resistance increases.  Air is just fine when you just let it move at will.  It can become amazingly strong as any building that has met a hurricane or tornado can attest to.  And as objects like asteroids and space capsules hurtle through the atmosphere they burn up!

ASHRAE 62.2 requires bathroom fans to make no more noise than a quiet refrigerator in a quiet kitchen: 1 sone or less.  And if you put an Energy Star bathroom fan on the bench and plug it in, you can barely hear it.  It’s amazingly quiet.  “Is it running?” people ask.  And it is.  So how come once you install the fan in the ceiling it gets uncomfortably loud?

Fan manufacturers not only made these fans quiet, they put DC motors in them that are extremely tolerant ofchanges in pressure.  As the pressure increases in the installation, the fan motor compensates by using more power to increase the speed of the spinning wheel that is pushing the air.  (Notice the curve on this graph that starts on on the left side and then drops off the cliff at about 75 cfm.  It has about the same airflow from 0.45 iwg as it does at 0.0 iwg!)  That’s a wonderful thing because people can install the fans horribly and step on the duct and lots of other nasty things and still come out with the same airflow . . . but not the same sound level.  What was really, really quiet is now uncomfortably loud.  And as houses get tighter they get quieter and a noisy fan is annoying which is why so much effort was made to get them quiet so they could run all the time without bothering anyone!

I have found that builders get aggravated because these quiet and expensive fans that they have been compelled to install really aren’t all that quiet.  And they should be quiet.  They have been designed to be quiet.  Tested to be quiet.  And if you disconnect them from the installation, they are quiet.

So here’s a simple way to determine if the fan is working right: listen to it.  If the air is angry, it will be noisy and noisy DC fans equal bad installation.  The air is yelling at you.  I have found ducts filled with the foam that was sprayed on the house for insulation.  Backdraft dampers remain taped closed.  Ducts terminated against a wall or floor in the attic and don’t actually get to the outside.  If a bathroom fan that is rated to be < 0.3 sones is noisy, its a bad installation.  Period.  Fix it.  It may still be moving enough air to meet the ventilation requirements, but if it is noisy the homeowner will find a way to turn it off and stuff it full of socks.  Then the air in the house will get bad and people will get sick.  And the occupants will get angrier than the air!  And the really dumb thing is that all these codes and standards and mathematical computations and formulas to size the fan correctly mean absolutely nothing if the fan is turned off.

Should a homeowner have control of the ventilation system?

January 25, 2014
Brightened Circuit 2

Sophisticated Control

Allison Bailes started this discussion on his Energy Vanguard site.  (Go to http://bit.ly/LRL43Q)  I was going to respond there, but there wasn’t enough room.  I used to build sophisticated controls that would do all sorts of wonderful things, but they got complicated and expensive.

You can feel the heat from a heating system.  You can feel the coolth from the air conditioning system.  You can see the change in daylight and know when you should turn on the electric light.  You can’t see or smell radon or carbon monoxide or PM 2.5 particles.

Heat is needed when it’s cold.  Cooling is needed when it’s hot.  Ventilation is needed . . . when?  When the bathroom is smelly?  When the bacon burns?  There is no one, single marker or flag for mechanical ventilation.  If there was, it would be simple to answer the question, “Should a homeowner have control of the ventilation system?”

So if a homeowner is going to control his or her ventilation system, how would he or she do it?  Manual control through an on/off switch perhaps coupled to a light in a bathroom?  This approach is equivalent to an occupancy sensor.  I did some tests of ventilation controls a number of years ago, and a manual control like that had exactly the same impact on the humidity in the bathroom as having no fan at all.  No impact.  Might as well not have a bath fan as far as humidity is concerned if you’re going to control it with a light switch.  It might have some impact on methane, but I don’t have the data on that.

Manual ventilation control will not work well because we can’t tell people when they should turn the fan on and when they should turn it off.  And when (or if) they ever turn it on again.

So that leaves the alternative of automatic control.

A standard humidity control will turn the fan on when the humidity rises above the set point.  What’s the set point? 70% RH (like 70 degrees F)?  55% or 30%?  Do you change the set point seasonally?  Do you change it on the same days every year like the change in daylight savings time (or putting fresh batteries in the smoke detectors)?  Will the fan run all the time in hot humid weather?  In my control tests, a humidity control that was set to turn the fan on at 43% RH and off at 41% RH ran for 20 minutes on the day that I tested it.  If I had set it to turn on at 41% RH and off at 38% RH on the same day, it would have run for 9 hours.  Relative humidity is difficult to explain under any conditions, but constantly adjusting the RH set point is not an effective way to control the ventilation system.

CO2 might be good for occupancy, but it is certainly not the only reason to ventilate a house.  I built a ventilation control that used a mixed gas sensor.  We called the “Flatustat”.  Works great.  The one in my bathroom has been operational for the past 20 years or so.  We could create a control that responded to a any number of IAQ conditions, but they would be expensive, and it is difficult enough to get people just to invest in mechanical ventilation in the first place.  Price is definitely a barrier.

So how about quasi-occupant control with a timer?  How should it be set?  The ASHRAE 62.2-2013 Standard says that if you’re going to run the fan half the time you need twice the airflow.  If you’re going to run the fan one third of the time, you need three times the airflow.  If you’re going to go beyond a three hour on/off period, you’re going to need to do some more calculations which depends on the ventilation effectiveness and air turnover and the fan gets really big.

But why do that?  The energy saved for most systems by shutting them off for part of an hour or even three hours, is small.  You could save energy by shutting off your clock when you weren’t looking at it. You could save energy by shutting off your doorbell when you weren’t expecting company.  Doorbell transformers use power just sitting there.

So why not just size the fan to meet the 62.2-2013 Standard and let it run all the time?  There is some weird psychological barrier to this really simple, basic, least expensive and logical solution.  The Standard says you have to give the occupant control so they can shut it off.  It’s their house.  They should be able to shut things off that they don’t want running, but there probably should be a sign warning of the consequences if they do that.

Someone once told me that the first thing many people do when they walk in the door of their home is to turn the TV on.  Maybe the ventilation system should be controlled by the same switch.  Turn on the TV.  Turn on the ventilation system.  I’m glad that wouldn’t work for everybody.

You could think about the ventilation system as a scuba tank.  When you’re under water, you wouldn’t want to shut your air off for any period of time.  When you’re in a house (a contained volume of air that is continuously being polluted by waste air from people and possessions), you’re effectively under water.  Don’t shut off your air.  Keep it simple.  Take a deep breath.  It’s okay to let it run.

Check out our website: http://www.heyokasolutions.com/

Coming soon: Average and Effective Air Change Rates: One Limburger at a Time

Should a homeowner have control of the ventilation system?

January 24, 2014
Brightened Circuit 2

Sophisticated Control

Allison Bailes started this discussion on his Energy Vanguard site.  (Go to http://bit.ly/LRL43Q)  I was going to respond there, but there wasn’t enough room.  I used to build sophisticated controls that would do all sorts of wonderful things, but they got complicated and expensive.

You can feel the heat from a heating system.  You can feel the coolth from the air conditioning system.  You can see the change in daylight and know when you should turn on the electric light.  You can’t see or smell radon or carbon monoxide or PM 2.5 particles.

Heat is needed when it’s cold.  Cooling is needed when it’s hot.  Ventilation is needed . . . when?  When the bathroom is smelly?  When the bacon burns?  There is no one, single marker or flag for mechanical ventilation.  If there was, it would be simple to answer the question, “Should a homeowner have control of the ventilation system?”

So if a homeowner is going to control his or her ventilation system, how would he or she do it?  Manual control through an on/off switch perhaps coupled to a light in a bathroom?  This approach is equivalent to an occupancy sensor.  I did some tests of ventilation controls a number of years ago, and a manual control like that had exactly the same impact on the humidity in the bathroom as having no fan at all.  No impact.  Might as well not have a bath fan as far as humidity is concerned if you’re going to control it with a light switch.  It might have some impact on methane, but I don’t have the data on that.

Manual ventilation control will not work well because we can’t tell people when they should turn the fan on and when they should turn it off.  And when (or if) they ever turn it on again.

So that leaves the alternative of automatic control.

A standard humidity control will turn the fan on when the humidity rises above the set point.  What’s the set point? 70% RH (like 70 degrees F)?  55% or 30%?  Do you change the set point seasonally?  Do you change it on the same days every year like the change in daylight savings time (or putting fresh batteries in the smoke detectors)?  Will the fan run all the time in hot humid weather?  In my control tests, a humidity control that was set to turn the fan on at 43% RH and off at 41% RH ran for 20 minutes on the day that I tested it.  If I had set it to turn on at 41% RH and off at 38% RH on the same day, it would have run for 9 hours.  Relative humidity is difficult to explain under any conditions, but constantly adjusting the RH set point is not an effective way to control the ventilation system.

CO2 might be good for occupancy, but it is certainly not the only reason to ventilate a house.  I built a ventilation control that used a mixed gas sensor.  We called the “Flatustat”.  Works great.  The one in my bathroom has been operational for the past 20 years or so.  We could create a control that responded to a any number of IAQ conditions, but they would be expensive, and it is difficult enough to get people just to invest in mechanical ventilation in the first place.  Price is definitely a barrier.

So how about quasi-occupant control with a timer?  How should it be set?  The ASHRAE 62.2-2013 Standard says that if you’re going to run the fan half the time you need twice the airflow.  If you’re going to run the fan one third of the time, you need three times the airflow.  If you’re going to go beyond a three hour on/off period, you’re going to need to do some more calculations which depends on the ventilation effectiveness and air turnover and the fan gets really big.

But why do that?  The energy saved for most systems by shutting them off for part of an hour or even three hours, is small.  You could save energy by shutting off your clock when you weren’t looking at it. You could save energy by shutting off your doorbell when you weren’t expecting company.  Doorbell transformers use power just sitting there.

So why not just size the fan to meet the 62.2-2013 Standard and let it run all the time?  There is some weird psychological barrier to this really simple, basic, least expensive and logical solution.  The Standard says you have to give the occupant control so they can shut it off.  It’s their house.  They should be able to shut things off that they don’t want running, but there probably should be a sign warning of the consequences if they do that.

Someone once told me that the first thing many people do when they walk in the door of their home is to turn the TV on.  Maybe the ventilation system should be controlled by the same switch.  Turn on the TV.  Turn on the ventilation system.  I’m glad that wouldn’t work for everybody.

You could think about the ventilation system as a scuba tank.  When you’re under water, you wouldn’t want to shut your air off for any period of time.  When you’re in a house (a contained volume of air that is continuously being polluted by waste air from people and possessions), you’re effectively under water.  Don’t shut off your air.  Keep it simple.  Take a deep breath.  It’s okay to let it run.

Check out our website: http://www.heyokasolutions.com/

Coming soon: Average and Effective Air Change Rates: One Limburger at a Time

Sleepy From Turkey CO

November 26, 2013

I have been forced to leave more houses during energy audits because of gas ovens than for any other reason.  A gas oven burns gas.  Anything that burns can generate Carbon Monoxide or CO.  The combustion fumes move up through100_2776 an opening or chimney that generally vents just below the control panel near the burners.  If you hold your hand there, you will feel the warm, moist combustion air leaving the oven.  If the oven is old, dirty or mis-adjusted, an excessive amount of CO will get produced when the oven is being used.  The CO level is particularly high when the oven is first turned on (commonly over 1,000 ppm)  and should decrease as the system achieves a steady state operation (dropping to around 100 ppm or less).  It is advisable to keep the range hood running and venting to the outside or a window open slightly while using the oven.  CO has about the same molecular weight as oxygen so it is neutrally buoyant, but I would keep the infants out of the kitchen while the oven is warming up.

A well-adjusted gas oven flame should be blue in color, symmetrically shaped, and about ½ inch tall.  A ragged, hissing flame indicates the combustion process is getting too much air.  A yellow orange flame indicates it is getting too little air.  The flame should be continuous along the length of the burner.   If it’s not, some of the ports may be clogged, but make sure the oven is turned off and cool before making any adjustments.

I have always heard that people get sleepy from the tryptophan in the turkey, but I have begun to wonder if it’s the CO from the oven!  Enjoy Thanksgiving, but make sure your kitchen is properly ventilated!

Please visit our website: http://www.HeyokaSolutions.com

Measuring Airflow through a Return Side Tap

March 16, 2013
Image

Averaging Flow Sensor

I’m putting together an advanced on-line residential ventilation course for GreenTrainingUSA, and in the process a couple of issues came up.  One of these is testing airflow on the supply pipes to air handlers.  This popular approach includes a pipe from the outside of the building attached to the return side of the air handler.  The opening can be controlled by a damper that opens when the air handler turns on and air is drawn into the air handler along with the return air from the house.  It gets circulated around the house, blended with the other air.  Some of these systems include a control that monitors the run time of the air handler.  If the air handler does not run long enough to satisfy the ventilation requirement, the control restarts the air handler just for ventilation.  Some of these controls also monitor the outside air humidity and temperature, overriding the ventilation operation if it is too cold or too humid outside.

This approach effectively puts the house under positive pressure.  The pipe to the outside is like a hole in the return side of the HVAC system and since more air is being sent to the house than is being removed from the house by the air handler, the house is effectively under positive pressure.  The question is: How much air is being drawn through that pipe into the house?

It is often difficult to measure the flow into the system from the outside of the house either because of the location of the exterior hood or because of the irregular surface of shingles or clapboard or brick.  A measuring instrument that is sensitive to air motion is likely to be impacted by air movement on the outside of the house.

Drilling a hole in the ducting and measuring the pressure when the air handler is running, will provide the static pressure in the ducting.  Let’s say that produces – 5 Pascals of pressure.  The duct can then be disconnected from the exterior hood and a duct tester can be attached to the pipe.  Turn the air handler on again and then turn on the duct tester fan and increase the flow until there is – 5 Pascals of pressure.  At that point, the air moving through the duct test fan will be equal to the air moving through the ducting when the system is operating under normal conditions.

A simpler way to approach this is to get a small flow station and insert it into the ducting.  I recently found some remarkably inexpensive ones from Dwyer (Series PAFS-1000).  The one for 4” ducting is $7.25 and the one for 6” ducting is $8.50.  These work like simple pitot tubes.  You need to drill a 7/8” diameter hole for the sensor.  Insert the sensor into the duct and attach Channel A of your manometer to the two taps and read the pressure.  Use this process:

 

Air movement through a duct measured with a pitot tube (or averaging flow sensor):

VP = TP – SP (ΔP in Pascals)

FPM = SqRt(VP) x 253.29

CFM = A x FPM

Where:

VP = velocity pressure in Pascals

TP = total pressure in Pascals

SP = static pressure in Pascals

FPM = feet per minute

CFM = cubic feet per minute

A = area of the duct in square feet

So, for example, if you get a pressure reading of 1.3 Pascals and it is a 4” diameter duct, because you are looking at the pressure difference between the two ports, that is the velocity pressure or VP.  The FPM velocity is the square root of 1.3 times 253.29 or 329 feet per minute.  The area of the duct is 0.087 square feet, so the CFM equals 29.  This process is not perfect, but it’s a lot easier than trying to measure the flow from the outside or the duct tester approach.

We need to get better data on the performance of this ventilation approach.   29 cfm wouldn’t meet many of the ASHRAE 62.2-2010 requirements even if the air handler was running 24/7.

Visit our Website at http://www.HeyokaSolutions.com

Ventilation and Health

January 31, 2013

Sleeping StudentThere are a lot of grumblings about a requirement to add mechanical ventilation to homes.  When we gather around the campfire on a starry night, there isn’t a need for mechanical ventilation.  When we bring the campfire into the building, we a flue to take the smoke and pollutants out.  And we also bring a lot of other things into the house including the dogs and cats.  And we cook in the house and generate a lot of moisture by taking showers.  We even bring plants inside to make it feel like we were still outside.  And we tighten up the house to keep it warmer in winter and cooler in summer.  So we’re not out under the starry, starry night any longer.

Okay, but is the indoor environment really hurting us if we don’t have mechanical ventilation?  In a dry climate like Nevada, is there really enough of a humidity problem to need mechanical ventilation?  Although it is difficult to study the relationship between mechanical ventilation and health, studies do exist.  Just this morning on MSN there was an article about “20 things that are making us dumber”.  Along with “Honey Boo Boo” and excessive email that we have to check on our “SmartPhones” every 90 seconds, was “Poor Ventilation”.  The article said, “Excess carbon dioxide is doing more than wrecking our climate – it’s also making us stupid.  Researchers at Lawrence Berkeley Livermore slowly increased the amount of CO2 in a poorly ventilated room while college students attempted to solve a series of complex, strategic problems.  Not surprisingly, the more CO2 in the atmosphere, the more mistakes the test subjects made.”

In a paper in Indoor Air entitled “Ventilation rates and health: multidisciplinary review of scientific literature”, a group of very knowledgeable researchers reviewed 27 papers published in peer-reviewed scientific journals.  Their conclusion was that “there is biological plausibility for an association of health outcomes with ventilation rates”.  They also said that, “Home ventilation rates above 0.5 air changes per hour (h-1) have been associated with reduced risk of allergic manifestations among children in a Nordic climate.”

In another Indoor Air paper entitled “Association between substandard classroom ventilation rates and students’ academic achievement”, researchers from The University of Tulsa, the Illinois Institute of Technology, and the National Institute for Health and Welfare in Kuopio, Finland studied the relationship between classroom ventilation rates and academic achievement.  They determined that, “There is a linear association between classroom ventilation rates and students’ academic achievement”.

Pine Tree air freshenerSomething else to think about.  The global market for air fresheners is forecast to reach US$8.3 billion by the year 2015. Growing consumer inclination towards fragrance products such as candles for decorating their homes is poised to propel the air fresheners market.  [Global Industry Analysts, Inc.]  (Candles also put out CO.  I’m just saying.)  Air freshener advertising puts people in rooms with wrestlers and brags about how fresh it smells!  If there are no pollutants in our air, why are we spending so much money to cover them up?  In an article in the University of Washington News entitled “Toxic chemicals found in common scented laundry products, air fresheners” author Hannah Hickey says, “”Be careful if you buy products with fragrance, because you really don’t know what’s in them. I’d like to see better labeling. In the meantime, I’d recommend that instead of air fresheners people use ventilation, and with laundry products, choose fragrance-free versions.”  Her study showed, “58 different volatile organic compounds above a concentration of 300 micrograms per cubic meter, many of which were present in more than one of the six products. For instance, a plug-in air freshener contained more than 20 different volatile organic compounds. Of these, seven are regulated as toxic or hazardous under federal laws.”

I have a control on my own ventilation system that uses a sensor that was developed in Japan to react to the chemical soup emitted by cigarettes.  No one smokes in my house, but there have been numerous times when the control has activated the fan when I can’t smell anything foul in the air and I have to wonder why it is operating, but I’m glad it is.  Our homes are full of stuff that we shouldn’t be breathing.  Is it worth betting your long term health and that of your children to save the cost of a fan?

(Copies of these articles are available upon request.)

http://www.HeyokaSolutions.com

And Another Thing about Residential Ventilation

April 1, 2012

Now that the ASHRAE 62.2-2010 residential ventilation standard is so much in the fore front of residential energy efficiency, I have been trying to explain some of the more complex parts like the Infiltration Credit and the Existing Building Deficit from Appendix A.  I got so fed up with all the bits and pieces of this process that I have developed a spreadsheet that is available on our www.HeyokaSolutions.com website.  All you have to do is plug in the state or province where the house is located, select a city, enter the floor area, the number of bedrooms, and the number of stories.  The spreadsheet can then calculate the basic whole building ventilation rate from that, give you an ‘N’ factor based on the ASHRAE 136 weather tables, and give you a target ACH50 for .35 air changes per hour.  If you enter a starting CFM50, it will then use that information to calculate the adjusted whole building ventilation rate including the infiltration credit, and provide the ACH50 and the ACHnatural.  You can then plug in a Finish CFM50, and will give you the readjusted whole building ventilation rate.

If it is an existing building, you can plug in information about the kitchen and bathroom windows and fans, and it will give you a further adjusted whole building ventilation rate that will allow you to leave the existing fans in place.  It will also calculate the house depressurization based on the fan airflows.

And since the whole building ventilation system can be used intermittently, I have added a tab that can be selected to determine either the size of the fan required or the run-time depending on the desired operating cycle.  This spreadsheet is free because I want people to be able to apply the standard effectively without spending a huge amount of time on the math.  Check it out.

Also available on our website is a ASHRAE 62.2 checklist for analysts and auditors that will allow you to go through a home and determine what needs to be done to meet all the elements of the Standard.  It’s sort of like the whole Standard on one page.  There is also a system documentation sheet that will allow the designer of the system to meet the documentation requirements of the Standard and provide really useful information to anyone that comes along afterwards to check the system as well as information for the homeowner to know what their system is supposed to do and maybe understand why they should shut it off and stuff it full of socks!

Part 4: Time to Talk about Residential Ventilation – Selecting the System (cont.)

September 25, 2011

There are a lot of choices when it comes to installing a whole building ventilation system.  The system has to be quiet or people won’t use it.  It must be serviceable for both the motor and, if applicable, the filters.  And it must be energy efficient.

QUIET FANS:  That car alarm that doesn’t shut off, the woodpecker hammering on the top of the chimney, the jackhammer on the street – none of us do well with annoying noise.  The ventilation system in the house has to be virtually invisible to the ear.  It has to perform the task of changing the air as quietly as your breathing, at least as quietly as the refrigerator.  A quiet refrigerator in a quiet kitchen is the definition of 1 sone of sound level.  ASHRAE 62.2-2010 requires that the whole building fan operate at 1.0 sone.  If it isn’t quiet, the occupant of the home will seek it out and shut it off.   If it’s not running it’s no use at all!

Courtesy of Panasonic

EXHAUST-ONLY:  You might choose an exhaust-only system for the simplicity and the relatively low cost.  It can be as basic as a centrally located bath fan, venting to the outside, relying on leakage into the house for make-up air, hard wired to run 24/7 or perhaps with a control to operate part of every hour.  The primary drawbacks are that there may be parts of the house that don’t get a lot of fresh air and that these systems rely on putting the house under negative pressure, randomly sucking air in through the building system.  In the scheme of things, these are relatively minor drawbacks.  Operating cost is surprisingly small.  The energy efficient bath fans that  are available can draw less than 20 watts – less than the light bulb in the refrigerator, typically less than $20 per year.  The annual conditioned air cost is also quite small – roughly equivalent to the airflow volume times $1. about $60 per year for a 60 cfm fan.  Total cost for a year to breath – about twenty-two cents per day.

SUPPLY-ONLY:  The supply-only systems are harder to find.  They work in the opposite direction than the exhaust-only, pressurizing the house and allowing the air to leak out through the building shell.  They can be as simple as adding a pipe to the outside connected to the return side of a central air handler blower.  Whenever the air handler turns on, fresh air is drawn in and distributed around the house.  A control can be added to the air handler so that it operates periodically just for ventilation.  The benefit of this approach is that the air can be fully distributed.  The down-side is that the air handler blower uses a lot more electricity to operate than a small bath fan.  Another down-side is that the house is pressurized and warm, moist air can be forced into the building shell components which is not a great idea in a heating dominated climate like Maine or Ohio.  If the air handler blower is efficient, the operating cost can be reasonable.

BALANCED WITH HEAT OR ENERGY RECOVERY:  These devices are designed to be balanced.  They should draw into the house the same amount of air they blow out of the house.  Ideally they should have their own, dedicated ducting system, drawing the air out of the bathrooms and putting the fresh air back into the bedrooms or other highly occupied spaces.  If the  house is particularly tight, these systems are the way to go.  They don’t rely on leaks or holes to let the air in or out.

Courtesy of Venmar

An ERV exchanges both heat and moisture.  So in a heating dominated climate when the air outside is cold and dry relative to the inside, more moisture will be retained in the house because it will be brought back in by humidifying the incoming air stream.  For that reason, an HRV may be better in a heating dominated climate.  In a cooling dominated climate, the outside air is hot and humid.  An ERV will reject some of that humidity by adding it to the cooler and dryer outgoing air stream.  So an ERV has some advantages in a cooling dominated climate.  Go to the HVI web site and check out the Product directory.  The power consumption and the efficiency of these units is listed there.  Compare the “Sensible Recovery Efficiency” numbers to compare units.

Even though HRVs and ERVs save energy by preheating or precooling the ventilation air, they commonly use more energy because of less than optimum efficiency motors.  That problem is exacerbated when they are connected to the air handler for distribution.