Fresh Air for Conditioned Shop

[Jace817]

I am in the early planning stages of my new workshop. I am building a 30' x 50' woodworking shop that will have a small loft for an office. I'm located in North Texas, and plan on conditioning with mini splits. I will have a dust collector system and air scrubbers, but I'm trying to decided what to do for fresh air. I plan to make the building pretty tight.

My thought is that I will need a system that can either operate in two modes, or two different systems. But for the most part will need to run in a normal low for general light woodworking or assembly where the dust collectors and air scrubbers keep it where it needs to be. But there will also be times when doing something that creates some relatively light fumes or dust where more air exchanges will be needed.

Any suggestions? Not too terribly concerned with heat recovery in the winter, but I am concerned with overpowering the AC in the summer.

For anything really noxious, I have a separate smaller shop where I do my automotive, spray finishes, and welding in separate from this space.

 

[Blueshound_GJ]

Maybe a fresh air heat exchanger? I've always been curious about using them in a home application.

 

[dcg9381]

I've been building homes with foam insulation for years. The need for fresh air subject seems to be somewhat open to opinion here in Texas. I say Texas, because we run our HVACs so much that humidity is not typically a problem.

The low-tech way to do it is to add a simple "outside air" intake (when you use traditional HVAC). This was as simple as an electrically controlled valve on one of my homes that allowed the air handler to pull in "fresh" air off the roof. I'm sure that air was about a billion degrees. I eventually disabled it. I did not notice any difference.

Homes up north get more fancy systems. I've seen ultra-air and other vendors. They're often de-humdification systems in addition to fresh air, as up north heating seems to increase moisture.

I've never paid much attention to "air quality" although I'm aware that recommendations are that you have enough air flow to turn over the house volume about 4x per day.

Existing house and shop - both on foam insulation. I did nothing. No issues. The shop though, with roll up doors it's not exactly a tightly sealed space.

There are some pretty good systems with advanced controls on run timing, can trigger by humidity, etc... I have not used them, but I've seen them installed.

In a wood shop, I'd start by treating it like a wood shop with a whole shop filter in addition to vaccum on the power tools...

I think this isn't an exact science.

 

[fitter30]

Not a fan of using mini splits in dirty/ dusty environments because they use enhance fins on both indoor and outdoor units. Fins have small slits in them, close spacing and wavy. With their thin filter and cleaning of the coils/ blower wheel they can be a pain.
Look at a you tube cleaning a mini. Fresh air could use EVR Energy Recovery Ventilator or a simple electric damper wire to the exhaust system. Look at raised lance and louvered fins.

Evaluating Fin Enhancements for Heat Exchangers | The Super Blog

Learn about the various materials used for heat exchanger fins, & the benefits & tradeoffs of corrugated, flat, sine wave, raised lance and louvered fins.

www.superradiatorcoils.com

 

[MBR2000]

In our 3-year old home here in north Texas, apparently code requires a fresh air intake, because new construction houses are much tighter these days. Mine pulls air in from the patio ceiling, and I assume the duct is connected to the return plenum on the air handler. I don't know if there is a electronically-controlled damper, or how it would work. But it would not make sense to draw in outside all the time. Has to be some way to balance air quality with energy efficiency.

 

[DC73]

I'm trying to decided what to do for fresh air. I plan to make the building pretty tight.

You could research HRVs (heat recovery ventilators) and ERVs (energy recovery ventilators). Probably the priciest option but I'd bet someone makes something that would work for your needs.

The simplest option would be an exhaust ventilation system whereby you used something akin to a bathroom exhaust fan. But, with your tight building, the air would have to come in from somewhere and if the building is very tight, you'll likely need an intake for outside air. You could put the exhaust fan at one end of the building and the supply intake at the other. Should be able to figure out how to use electrically operated dampers at both ends so the intake and exhaust can stay closed when the exhaust fan is not operating. You could put the exhaust fan on a timer and run it manually. You might be able to find a way to wire it so that it operates only when the mini-splits are operating. Might need the help of an electrical/electronics guru who can help you figure out how to wire the system to operate like you want but I'd bet you can find that kind of help on this forum.

Another thought is to visit the Green Building Advisor website and ask your question on their Q&A forum. They have a lot of energy geeks who hang out there who might have different ideas as to how to pull this off. https://www.greenbuildingadvisor.com/

Good luck,

DC

 

[PoorUB]

My thought is that I will need a system that can either operate in two modes, or two different systems. But for the most part will need to run in a normal low for general light woodworking or assembly where the dust collectors and air scrubbers keep it where it needs to be. But there will also be times when doing something that creates some relatively light fumes or dust where more air exchanges will be needed.

How much air are you exhausting outside? Anything you blow out, needs to be replaced. Air you dust collectors dumping outside? Any large exhaust fans blow to the outside?

Until you know the CFM of air dumping to the outside there is no way to answer your questions.

 

[Denwood]

Take a look at ducted mini split systems (same tech as ductless but with an air handler) so you can sort filtration out correctly. Otherwise you'll be pulling mini split heads apart for cleaning quite often. Some options here: https://www.mitsubishicomfort.com/r...lli-air-ducted-solutions#scrolled?modelID=SEZ

It makes far more sense to use a ducted system with return filtration in a shop so you can just swap intake filters rather than pulling mini splits apart for cleaning.

Case 1, Office only:

In North Texas, you can take a look at the Panasonic FV-04EV1 which will be fine for an office, assuming your loft will be isolated from the shop? It has an ERV core so will be useful to maintain inside humidity levels. It is well suited to warmer climates like yours.

Panasonic Canada - Home

na.panasonic.com

It's one of the lowest cost solutions you'll find for a small space. I have used these personally and although not crazy efficient, it will get the job done. If you're building tight, you'll want air exchange.

Case 2, entire space:

If you do want to use a larger ERV for the entire space, take a look at the Renewair EV Premium L : https://www.renewaire.com/erv/ev-premium-l/

That unit is one of the best you'll find with respect to price vs efficiency. You can find other units listed here with efficiency: https://www.hvi.org/hvi-certified-products-directory/section-iii-hrv-erv-directory-listing/

You will for sure want to also sort inline filters for a unit like these as the internal ones are not practical for a shop. I use these ones as they are cost effective, but it's quite easy to fab up filter boxes DIY as well: https://hvacquick.com/products/resi...CQuick-CFB-Series-MERV-13-Inline-Filter-Boxes

In most cases you'll want enhanced filtration on fresh supply air (from outside) but in a shop, I'd also be installing MERV 8-10 on outgoing stale air to keep dust out of the ERV core.

 

[jochute]

I am in North Texas as well, I have mini splits in my shop and I wish it was a ducted system running something like a 20x4 filter maybe with a prefilter. Even using a festool vacuum at every tool and air scrubber the mini splits just can't handle it. There is no air filtration. Starting from new I would go ducted, maybe ducted mini split. If the building is a metal building with any roll up doors I don't see how it can be tight enough to necessitate a fresh air system, even with spray foam.