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3799 Main St. #87024
Atlanta, GA 30337
USA

773.398.5288

Advanced residential construction and home improvement consulting and owner's advocacy in Atlanta, using the latest building performance diagnostic and modeling techniques and tools. Airtightness, insulation, HVAC, ventilation, moisture, and air quality and EMF consulting for homeowners and building professionals alike.

Videos/Podcasts/Articles

Home performance articles and stories from the field with internationally respected building forensics guru Corbett Lunsford at the Building Performance Workshop. Hear new episodes of the Building Performance Podcast, see new videos from the Home Performance YouTube channel, and learn all about how diagnostic testing (more than an 'Energy Audit') can make home improvement and new home construction a proven process!

Filtering by Category: Dear Corbett

Building Science Podcast features HOMEChem

Corbett Lunsford

Corbett and Kristof Irwin from Positive Energy Austin dive deep into the revolution that's brewing. Building Science will never be the same after the HOMEChem Experiment shows us the 4-dimensional chess game that's happening at a molecular level inside every building and vehicle in the world.

Subscribe to the Building Science Podcast on iTunes or any other podcast platform. More at: https://positiveenergy.pro/building-science-podcast/2018/9/20/0asmwbpk31r3ced6myrqjjeg9smvy4

DEAR CORBETT: Multifamily Blower Door Testing Nuances

Corbett Lunsford

Good day Corbett,

I wanted to let you know, that I really enjoy your approach to the whole building science and your building performance workshop website. I am relatively new as a Resnet Rater and the county where I live is Collier County in Florida.

They recently adopted the new code standard set by the state. My question relates to multifamily condo units. I have a client that did renovations to a 2,500 sq. ft. penthouse condo and the front door to the unit is I a common area. The county wants them to perform a blower door test in order to obtain their certificate of occupancy.

I realize this would be a compartmentalize test, since I can only have access to the unit they renovated for their client. Knowing that I will encounter not only leakage to outside but also internal leakage between units. I was wondering what the best approach would be to ensure a successful test. Collier County requires between 3 ach and 7 ach for a test to pass code.

Any information would be appreciated. Thanking you in advance.

Best Regards,
Norm Giguere
www.blowerdoorenergyexperts.com


Dear Norm-

Thanks for your question, it's a good one! First off, you should be fine if they did a good job with the renovations- 7 ACH50 is not terribly hard to achieve.

When you set up your blower door at the front door of the condo, you'll blow air out into the common hallway, so you want to make sure all possible windows/doors in that hallway are open to the outdoors. Use the emergency exits if necessary (make sure maintenance knows what you're up to).

You'll be testing the condo's leakage to everything outside of it, including the downstairs unit, but that's intended. They really will have air leaking between the two condos, if there are leakage pathways, and you want to be testing for that and including it in your blower door test result.

Ask your code official if they want the result to pass the residential code or commercial code, because you have to test at 75 Pa in commercial. I always advise doing a multipoint test (get the flows on at least two pressures, like 25 Pa and 50 Pa) so you can extrapolate the 75 Pa if anyone ever wants it in the future. Saves you a trip.

AS AN ADDED BONUS, consider doing a Zonal Pressure Test on the unit downstairs, to see how much the blower door is affecting it. Always nice to have more data than you need.

Happy Testing,
Corbett

DEAR CORBETT: HVAC Equipment Airflow Frustration

Corbett Lunsford

Dear Corbett,

I was going thru the videos in the training portal. Overall, I like your videos. However, every now and then, a portion of one leaves me less than satisfied with the answer. Usually, my disatisfaction is because you are rushing through and just skimming the details and explainations. I realize that your trying to limit the video's length and accept it.

However, I found one video that had something that you brought up, but didn't explain that frustrated me enough to write. The video is in the training portal, 'Mastermind Series Jan 2015' at 30:01 minutes in. Your talking about system airflows and you bring up NCI. You go to say how they add up supply airflows, return airflows, and compare it to what the airflow should be to get leakage. You say that that is wrong but don't explain. You finish by saying that system airflow needs to be measured at the blower. 

So, the question I have is: Are you objecting to comparing either the supply or return airflows to what the system airflow SHOULD be (i.e. not measured) or something else?

Would you agree with the following? 
(Equipment airflow) - (sum of supply register airflow) = (supply side leakage)
(Equipment airflow) - (sum of return register airflow) = (return side leakage)

Equipment airflow to be measured at or near the blower by one of the several methods. I am calling it equipment airflow and not system airflow just to be clear that it is what the fan actually produces.

Finally, are you doing full manual J's or just block load calculations to get ballpark numbers?

Thanks,
TJ

-_-_-

Dear TJ-

Great question, and I'm happy to clarify what I meant! Thanks for letting me know when my broad strokes don't actually answer your question and leave you frustrated- I always want to give a full picture of what home performance testing actually means.

My issue with measuring the supply airflows and return airflows, and inferring duct leakage from that is:

  1. How do you know what airflow the equipment is producing unless you measure the actual airflow at the equipment? You can use a calculation like 400cfm x tons of A/C, but what if it's heating season, 20 degrees outside, and the NEST thermostat won't let you disable the compressor's service disconnect and still run the air handler? Also, what if the installer targeted 350cfm per ton, or 450cfm?
  2. Even if you measure the equipment airflow, you won't be measuring the equipment cabinet air leakage, which is almost always there. In fact, the IECC duct leakage test assumes that 25% of all the duct leakage will be in the cabinet in new construction.
  3. The only way to measure duct leakage is to perform a duct tightness test, or for a quicker and more localized look, perform a pressure pan test during blower door testing.
  4. Measuring airflow is notoriously difficult. What tool and technique are we using? Pitot tube has high user error, passive flow hood (balometer) is not accurate for residential grilles and low flows, and anemometers need to be corrected for net free area of the grilles. Lots to scratch your head about, and it turns out the best way to measure airflow in the 21st century is still a plastic garbage bag.

To answer your final question, if all you need is a ballpark number, a block load is fine, but I always do a full room-by-room load calculation if I'm being paid to do an actual Manual J.

Hope that helps, and keep the questions coming!
Looking Forward,
Corbett

Dear Corbett: Why Don't Homeowners Want It Done Right?

Corbett Lunsford

Dear Homeowners: please read and absorb what the quality contractors come up against with typical clients. This is part of why high quality construction and home improvements are hard to come by...

 --------

Hi Corbett,
Hate to bother you, but you said if I had aquestion to get in touch with you. Sometimes I feel like just throwing my hands up in the air and giving up; why did I read that article about making the heating system airtightback in 1992 when I started my HVAC business? And why six years ago did I bother learning about the whole house approach? There are times I wish I wasn’t disciplined and motivated to do things right.

If a customer just wants a new energy efficient furnace or A/C and is not concerned with all the other issues with the house, should I just give them what they're asking for and take their money? Knowing how easy it would be to do that, I just can’t lower my standards. Even companies that are doing 'whole home performance' now, I’m following behind them fixing some of their mistakes already.

I get people telling me about the problems they are having inside the house. The question I’m always asking the homeowner is, If I see some safety concerns or other issues would you like me to tell you? On a service call, the first thing I have to get right is the problem with the equipment, than I can let them know what I see with the whole house and heating/cooling system generally.

I’m always getting pushback on this: "my heating system is just 7 years old, everything's fine." And here I am, telling them it was not installed correctly, and that we have to start all over again.  Always running into oversized furnaces and air conditioners with undersized ductwork.

Not sure if I’m explaining things correctly to the homeowner as to what I’m trying to accomplish inside the house for them. It always seems to come down to the price. Maybe I have to do a better job in showing value to the customer?

Right now, looking at one job, the call was for high end air purifying filters. The homeowner told me the house is 4000 sq ft but might include the garage and it’s 8 years old. Their 5 year old son has allergy problems, $650.00 utility bill a month, a lot dust in the house. They have 181,000 Btu output for heating and 10 tons of cooling! Told the homeowner the first thing we should do is test the house and HVAC systems first before installing the filters. It apparently costs "too much" to fix the problems. Help?
Thanks,
Sal C.


Hey Sal-
Great question, and I feel your pain!  Sometimes it can seem like our clients actually prefer to hire mediocre contractors to do cheap home improvements that make things steadily worse in the house.  I promise you, though, that it's not true. Yes, I believe it's 100% about education and showing the value, and judiciously using the powerful marketing tools Fear and Sex Appeal to do so.

Keep at it. I'll keep an eye out for your success stories to come. 

Looking Forward, 

Corbett

Corbett's Conversation with Stephen Rardon, HVAC Guru

Grace McPhillips

Stephen Rardon, HVAC expert extraordinaire, came to the #TinyLab to talk about home performance, HVAC testing, and being a world-class consultant to homeowner and builder clients alike!

If you haven't already, CHECK OUT STEPHEN'S YOUTUBE CHANNEL- his is twice the size and following of ours!

How to Renovate a Home in Dallas- the RIGHT Way

Corbett Lunsford

Dear Corbett-
I am not a contractor, but a residential homeowner that has become increasingly interested in owning (and taking a part in creating) a high performance building. After going through several series of podcasts, I ran across yours, and immediately loved it because you went into greater detail about the things that I want to learn about; so I want to thank you for the podcast.
Onto my situation.... I am looking to buy an older (1940's) home that has no hvac, next to no insulation, and needs a good deal of work; but I believe it has the best potential for making a high performance home.... a blank canvas.
What I am having trouble with is finding the local rock stars that can really help me make my house as efficient and comfortable as possible with my given budget. Do you know of any really good people in the Dallas area that could get me on the right track? Thanks again for putting out all the info!
~Derek R.


Thanks for reaching out, Derek! I'm always happy to help, and I think the home you're considering is a GREAT OPPORTUNITY. A blank canvas is much easier to paint on, and when a house is fully 'finished' and has been renovated, it just means you'll have to dig harder and deeper to find and fix the issues that are lurking under the surface.
I'll hook you up privately with a few of my own black belts who are part of Fall Fast Track, but I also want you to know that when we take this show on the road next year for the Proof Is Possible Tour, we'll be creating a directory of pros who pledge to deliver guaranteed results across the U.S.!  Stay tuned here for further developments on that front, and keep in touch about your high performance home renovation!
Looking Forward,
Corbett

How to Fix Summertime Heat on Your Top Floor

Corbett Lunsford

Hi Corbett-
Finally, I have two solid quotes for air sealing. I have one new concern, however. My finished attic gets really hot in summer, and the A/C dedicated to this attic rarely is able to cool the space below 82 degrees.  From what I have read, besides implementing some kind of reflective roofing material, the only way to keep an attic cool is plenty of airflow.  So, if we air seal the attic and add insulation (which I have read holds and radiates heat in summer ?), is this air sealing initiative going to make my attic unlivable in the summer?
Thanks!
R.L.


Hey there R-
First thing to do is stop thinking about your top floor as an attic of any type.  Yes, it used to be an attic, but now it's supposed to be inside the enclosure, so let's call it what it is- your valuable living space.
Not only will airsealing NOT going to make your top floor (finished attic) hotter in summer, it is in fact the ONLY THING that will make it cooler up there.  What's happening is called reverse stack effect: your air conditioners are creating cooler, drier, DENSER air, which sinks to the bottom of the house. All the air conditioning wants to be in the bottom of the house at the same time, so it creates a higher pressure down there, and there's a low pressure at the top of the house.
The cool, heavy air escapes through gaps and cracks in the bottom of the house, and the house now needs air, so it breathes in at the most depressurized (and also hottest) place- at the very top.  So all the air that's in your top floor rooms is coming from the attic spaces and the roof cavity.
Lastly, it's a total myth that attic ventilation will keep an attic cool- #1, attic ventilation is actually for venting MOISTURE, not heat; and #2, you don't actually care how hot it gets in your attic, since it's not part of your house.  The roofing manufacturers used to void their warranties if the attic got too hot, but they don't do that anymore.  You're free!
For a more detailed look at attic airsealing, watch this:

How to Master the Multi-family Blower Door Test

Corbett Lunsford

Hello Corbett,
A need to run a Blower Door test at a 3 house complex here in Greece. The houses are in the row, this means that normally I should have three Blower door devices, in order to measure the house in the middle. But I have only one Blower Door!
Additionally, I will need to hand over a written document (report), in order to certify the construction to the Passive House Institute. Do you have any suggestions?
Best and thanks in advance,
Stefanos


Hey Stefanos-
Great question! You do not, in fact, need multiple blower doors, because you actually want to include the unit-to-unit air leakage.  The measurement of all uncontrolled air leakage to outdoors and to other townhouses is a valuable one, and it should be the goal especially when building to Passive House (or PassivHaus) standards.  Watch this video for a visual explanation:

How Should a Homeowner Shop for a High Performance Home?!?

Corbett Lunsford

Hello Corbett,
I have been listening to your podcast and heard your request for ideas. You often mention the challenges in educating consumers, and I think my questions might be interesting to the non-professionals in your audience.
I just moved to Denver, Colorado and am considering purchasing a home for the first time. As a potential first-time homebuyer interested in air quality, moisture management, energy efficiency, and building durability, I expect that it is unlikely that I will be able to find a high-performing home at an entry-level price. With the expectation that I may need to invest in some retrofitting, I have a couple of general building performance questions:

Ascertaining current performance

Assuming that a first-time buyer probably will not have access to the sophisticated diagnostics described on your podcast during their search, what are some key things to look for that would indicate a high or low performance?
Utility bills can shed some light on energy efficiency, but how can someone gauge issues like air quality or moisture control?

Performance improvement opportunities

What factors influence a residential building’s suitability for a high-performance retrofit?
Are there factors that would influence the ROI of a retrofit for a modest home? And how could a homebuyer identify those?

Assembling a team

Do you have suggestions about how to assemble your team (realtors, inspectors, and appraisers) to help identify an entry-level home based on current or future potential?
What skills or expertise would you consider important?
Your podcasts have covered issues about financing for retrofits – so there may be nothing new to address here.
 
Basically, it would be great to be able to use a home performance lens during a home search to identify a property in which it is not too difficult or expensive to improve from decent to good performance.
As a potential consumer, I have enjoyed and learned a lot from your podcast. Thank you for thoughts.

Best,
B

I Turned My A/C Off All Day at 106 Degrees

Corbett Lunsford

Dear Corbett:

I thought I would send this your way.  I live in the Central Valley of California.  Yesterday it reached 106 degrees.  I did an experiment with my house.  My 1,883 sq./ft. house had a deep energy upgrade over three years ago.  The heating and cooling unit is a 2 stage/2 ton heat pump with no back-up heat.  The second stage of cooling is disconnected so I am cooling with 1.4 tons.  That is one ton for every 1,345 sq./ft.

Yesterday morning I left the house at 7:40 am.  It was 75 degrees in the house and 75 degrees outside.  I closed all of the blinds, turned the HRV off and turned the Heat Pump off.  In other words, I let the house float.  It got up to 106 degrees in Stockton yesterday.  Luci my bride got home at 5:40 in the afternoon and the house was 78 degrees.  She turned the thermostat back on and it brought the temp back to 75 in 30 minutes.

This stuff really works.
Keep up the GREAT work;
Dick Rome


Dear Dick-

You are awesome. I'm not sure I know many other home performance experts who have fixed their own homes- most of our families have to suffer at home while we help other people get comfortable. Thanks so much for sharing the good word!

~Corbett

How Much More Will a High Performance Home Cost?

Corbett Lunsford

The answer to this bass-ackwards question is: NEGATIVE DOLLARS AND ZERO CENTS. It costs LESS to build a high performance home, whether that means ENERGY STAR Home, a Passive House, a Zero-Energy Ready home, or any of a number of other green home certifications.  Here's why:

In his first Fall Fast Track week of 2015, home performance guru Corbett Lunsford answers the question "how much more will it cost to build my next home high performance?" The answer to the question is as straightforward as the question is ridiculous!

Dear Corbett: How Long Should My A/C Ideally Run?

Corbett Lunsford

Hi Corbett,
How long should the air conditioner run in a given day?  The upstairs zone was running for 16 hours yesterday, and 10.5 and 11.25 each of the days before.  Is that reasonable amount of time for the A/C to run given the recent summer temperatures?  We are still trying to get the developer in to fix the ductwork, and figured this might be an symptom of the problem.
Thanks,
Graham

Hey Graham!
Great question- your air conditioner is actually designed to run continuously when it's hotter than 89 degrees F outside.
The A/C's job is to both COOL and DRY the air, and if it's too big, it doesn't run long enough to wring the humidity out of the air. This leaves you with a muggy house, where you keep lowering the temperature to try to get comfortable.
So don't be concerned when your air conditioner runs for long periods on hot summer days- that means everything's working the way it's supposed to!
Looking Forward,
Corbett