Making your own blower door?

Has anyone attempted to make your own blower door system?

Making a small residential-use system doesn’t seem like rocket science to me but maybe I’m missing something.

  • Buy a manometer, gauge, controller
  • Build an adjustable door-frame with a fan opening
  • Buy a quality fan with an adjustable rheostat


I figured having a little $400-$500 blower door system with me would come in handy to show certain valued clients some of the aspects of an energy audit.

Why reinvent the wheel? The cost to build one correctly will likely excede the price of a manufactured unit that has been calibrated.

Your probably correct but I just hate the thought of spending $2k+ for a blower door with no immediate plans of going in the energy audit direction.

If I’m going to spend $2k for a calibrated door than I’m going to go ahead and get BPI certified. Considering I’ve spent over $9k in training and conferences in just the past 60 days, I’m gonna have to hold off for a bit on additional training.

I still have an incentive to promote BPI Energy Audits and a small inexpensive door would make for a good demonstration.

My main thoughts are why blower doors and water spray-racks are so freakin expensive. The nicer ones can cost you nearly $3k. I believe I could build an extremely nice blower door system for $1k or less.

The commercial spray rack I liked is made by Rain Maker and costs $3500. I’ve ordered the same aluminum, spray nozzles, tubing, a case, added additional features, and got a welder/metal worker lined up for the one I’m building at a fraction of that cost. It will also be calibrated EXACTLY the same per ASTM standards.

Just trying to improve upon the wheel that someone else already invented:mrgreen:

A box fan, some plastic and duct tape should do wnders for you

Brandon, I built one. I have had limited success with it.
I would love to chat with you about it.

I am in the office all day. If you email me I will send you my number. (unless you find it first)

I am thinking about making my own infrared imaging device by taping 12 infrared temp guns together and shooting them at a wall area to see if they all read the same temp. The guns with the lower temp indicate heat loss through lack of insulation or possible moisture. What do you think?

You have been waiting for the price to come down. Try it and let us know how that works…:smiley:

I bought one last month. Flir i5 for $1350.

A $500-$1000 door would be nice for Infrared scans for air leakage. I can see exspansive blower doors for energy audits and Air leakage values.

We need a Cheap blower door just to help IR pictures.


That’s exactly what I was thinking.

I just ordered some 6061-T6 1x2" (really light weight) aluminum rectangular tubing that can be telescoped with a slightly smaller inner-tube for the door frame.

Now I’m searching for a fan that will blow atleast 6300 CFM while also going down to 10 CFM. I’m going for building a really nice calibrated door since I’m already going through the trouble.

This project will be my Christmas holidays project. I am almost certain I can build a blower door just as good if not better than the Min***polis door for half the price. I may very well end up eating my words but I don’t see any harm in trying.

I’ll be sure to post pictures and results. If everything goes as planned, which it usually doesn’t, I’ll show you and offer you a quality door at a cheap price.


Your cost is going to be in the manometer. You can buy a cheap one for $150, but that is exactly what you will get.

A 1/2 way decent one is $500 and good ones are $1k plus. Even then you will only be looking at a 2 port one vs a 4 port on the blower doors.

You will have basically no shot with integrating the fan and the gauge. This requires custom software and programming.

Finally, throw out the word calibration. An NIST certification goes for $300 to $1k depending on the item. Not to mention the R&D you will have to do to prove it works correctly to them.

I know of other manufactures that have thought about getting in the market with Retrotec and Minneapolis and they don’t even want to horse with it, due to the initial costs.

Just buy one and spend your time on marketing to make up for the cost.



You make some good points. That’s the kinda info I was looking for. I figured there was gonna be some complications when it came to the “Calibrated” part. Seeing that blower door testing can factor into indoor air quality and human health concerns, I thought there might be some red tape.

I wouldn’t want to find myself in court explaining a home-made blower door so I may not aim for the truly “Calibrated” door.

I’ll most likely end up buying a Retrotec door in the Spring and move forward with BPI certification. On the other hand, I’ve started this project and I’ve come up with a really nice set-up so I’m gonna build a door just for the sake of enhancing Thermal Images.

I looked through your website and couldn’t find any manometers. Do you sell any average priced manometers or do you just sell the whole blower door packages? What about fans, got any of them?

I’m really liking that Fluke CO220 Carbon Monoxide Meter you have. I left my last $300 meter at someones house or it grew legs and ran away. I’m hesitant to buy another CO meter after speaking with another reputable inspector. He believes testing for CO’s goes beyond our general scope of inspection and is just asking for trouble. He makes a valid point but it’s still a nice tool to have.

The CO220 is a very good ambient solution, but even with the aspirator kit, it doesn’t do draft all that accurately.

I would recommend the Bacharach Monoxor III as a dedicated CO draft and ambient meter. The problem with it is it is not very compact, so putting it in your pocket like the CO220 is not really an option. Most guys go with a combustion analyzer and a compact ambient CO monitor.

It is funny you bring this up. I am actually in talks with some people to come up with a complete combustion safety and analysis standard for home inspectors. I really think it would be an easy add on to HI services. Eventually also adding on full on a full on IAQ standard. The public is much more aware now a days about IAQ, CO and combustion safety.

As far as a manometer, we have several, but I would stick with Testo and/or TSI/Alnor (higher end). When it comes to airflow meters it is tough to beat either of these manufacturers quality and accuracy. Plus they actually make their own devices.

Testo 510
Testo 512
Testo 521
Testo 526

The Testo 435-2 and 435-3 are both manometers as well as a host of other meters all in the same device. Really cool meter with the ability to calculate R and U value (never seen anything else that can do that).

Testo 435


Goodness!! You weren’t kidding! It goes from $150 bucks to $800 bucks. Where are the ones in between or like in the $250 range?

Would the Testo 510 do the job? I’m basically just wanting to know a close aprox. of indoor pressure and outdoor pressure. Just something to provide me with a way of knowing I’m close to the 50pa range for demonstrations?

Yes the 510 is a dual port manometer, but please realize it is a cheap manometer that I would probably not use for this purpose. However, it will give you the numbers you are looking for.

So here is another issue for you. The way a blower door works is by reading the air flow across the fan vs (WRT) the outdoors. How do you plan on getting the number across the fan? You could do an outside vs inside, but it is not the same thing.

You can keep this really simple if you are just wanting to negate stack effect, natural pressure +/- another 10pa or whatever, for the purposes of an IR scan. Make your frame. You can buy the cloth used in a blower door from us. I have some I can discount really cheap right now due to a customer that ordered 10 and then decided not to take them. They took a 25% restocking fee instead, so I can give you that discount. Then get yourself a fan from that is 26" across. You can then use the manometer (Testo 510) and tubing to get your indoor vs outdoor pressure. Before starting the door figure your natural pressure and stack effect pressure using the same manometer, then add 10pa to that so you get a natural negative pressure via the door that should be 10pa.

Here is another thing to keep in mind when doing an IR inspection and using a blower door. Let just take the example of a 50pa test concluding that the air change per hour (ACH) is 10. That means the air in the house changes out every 6 minutes. Now obviously that will not bring everything in to thermal equilibrium, but it does accelerate such. I have never quite understood why the standards proposed and passed do not really lay out the fact that the IR scan should be done at a much lower pressure (+10 or +5 pa plus stack and natural) to lower the ACH number so the Delta T is not eroded. Doing an IR scan after a 50pa or 75pa blower door test is pretty much worthless.

By the way lets do the math on your project:

Manometer - $150
Cloth $125 (ballpark)
Frame (not sure what you paid) $25
High Power Floor Fan ( - $250 (this one is 36", you need a 26" I couldn’t find one)

Professional look and feel for your customer -$2500 (lol)

Just buy a door already. :slight_smile:


Brandon, how much is your time worth?

No matter what the cost of building your own (insert name of precise technical measuring tool, here) might be, it’s uncalibrated and unreliable readings are worthless.

Try to convince someone that your home made moisture meter detects moisture behind the EIFS at the window and that they should tear it out for repair. How much would you pay your auto mechanic to hook your car up to his home made diagnostic computer…and pay for the repair work that it indicated to be necessary?

Get a blower door at ITC message board for $2000