I'm generally an overly generous landlord, but this is just sillyness. What I'm trying to provide is far better than most homeowners have. Do you think said tenants want to pay me more for providing exceptional level air quality?

Keep what air cleaner? They currently have a crappy 1" filter like most houses. I would be making their situation better than the already higher than most provide standard I'm giving them.

You seem to have bought into a bunch of snake oil there.

If you have people who can provide all those services for the few hundred that this would cost, please send me their contact info.

There would be no larger fan, just a larger media cleaner, which would slow the velocity through the filter and reduce the hit to static pressure. All of that is a good thing for both equipment and tenant. It also helps make up for often inadequate duct sizing, as the filter is often as much static pressure loss as the entire ducting system.

I can see that reasoning. I do try to stop by at least every couple months and take a look around the basement/common areas. All of my local properties I can do that w/o any notice to the tenants, so I just do it on a whim. I do also have a couple vacation rentals out of state, one with a forced air system… I'd like to just swap the filter, flush water heater out, do a pest treatment, etc quickly once a year when I visit there, rather than rely on my local managment to actually get these things done.

My tenants are generally pretty high end, and my units are mostly completely redone with new plumbing, etc, so not usually too many surprises and they will usually tell me if anything is off. But I do agree it's good plan to stop by and check periodically…

Your description only confirms my point. I have many landlord friends/associates, and have seen some things. In almost every case, I can point to where the landlord went wrong when something crazy like this comes up, plus a few just silly things that tenants didn't know any better but were trying. And my landlord friends who operate more like I do, much like me, have almost zero problems like this.

That's not to say you can spend infinitely and expect a return - of course not. But you do get back based on what you put in, and I can tell from your pictures, the way you talk about tenants, the things you expect of them, and the results you're getting, that you do not operate anything like I do. Your choice, but a lot of those results are things you should have expected rather than just complaining about the poor tenants you put in your places.

Anywhoo, I'm not providing crazy air filtration. I'm providing decent, better than average for a rental. And I'm looking to benefit myself and prolong my equipment life as well. Much more interested in productive input on my proposed plan than a tirade against tenants… anyone have more input on that?

GGross said:

@MTC

I am not sure if the larger/thicker filters would need replacing less often. In my experience I replace them at similar intervals to the thinner ones. I think some of the concern that a few might have with putting in thicker filters is that they are by default just a bit more restrictive to airflow, and so if they are not changed out in a timely manner they could get plugged a bit and cause your furnace some problems. I think that either route you take you are doing a great job. I used to rent from someone who refused to do any upkeep, and tried to bill me for the lack of maintenance when we moved out, so you are already leaps and bounds above many.

I would maybe add that the thinner filters, being overall less expensive, would make it cheap enough you could change them out more often, which could be seen as a benefit since minor issues can often go unnoticed and the more you get to see the property the more likely you may be to see an issue before it becomes a problem. But if you are able to get the thicker ones at a reasonable price, maybe you can stop by for a filter inspection the first year instead, to determine the correct interval to change your new filters

Thanks for being an active involved landlord, and sorry to see your thread get derailed here

I think you may be referring to something different than I am. Thicker filters of the same MERV rating offer drastically lower pressure drop and have drastically more filter area to allow for longer life with less pressure drop than thinner ones. Rough math - assuming same number of pleats (which is not usually the case, but just for simplicity sake), a nominal 1" filter is about 3/4" thick. The Honeywell F100 media is 4 3/8" thick. If same number of pleats, that would be almost 6x the filter area with no increase in air flow, contamination, etc, nor is the filter more restrictive.

I'm also looking to standardize my filter size up to a 20x25. Most of my furnaces currently have 16x20, 16x25, and I think one is already 20x25. So that increase in size at the filter would add a lot more media, while also slowing down the airflow rate since its going through a larger cross section of duct at that point, reducing pressure drop even further and extending life before clogging that much more.

I get the point of monthly-ish inspections. I do try to stop by my properties fairly often, but I have a couple of scenarios. My local ones I pop in a little more often, but often 3-4 months might go by, which the little 1" filters are not great for that. I have pretty great apartments which attract pretty great tenants, and for the most part, they're really good about letting me know if anything is off. The other scenario I have, and one of the places I really want to try to make this work, is a vacation rental I have 8 hours drive away. I'm usually there once a year over my kids spring break, and our management company is crazy expensive for general maintenance stuff. If I could get that one down to 1 change per year, or maybe 2, then I could do the one change, along with a bunch of other annual basic maintenance stuff for a few hours every year when I'm already there. If it seems like it needs more than that, could have the management do it once in the fall. Either way, should be getting really solid filtration and keeping the pressure drop way lower to protect the expensive HVAC equipment there, with minimal hassle/cost.

EdTheHeaterMan said:

Annual filter changes?

was the title of this post, and it struck me as being a little sarcastic. I don't know of any air filter that recommends anything less than 2 times a year, most are on a monthly or 90 day recommendation. So My question to @MTC is, Why do you want to do it once a year? Sounds like every other year might be OK if you can get a large enough filter in there. All you need is to get a 1000 ft roll of filter paper and connect it to a motor with a reduction gear. Have the paper connected to a paper shredder on the receiving end of the filter as it rolls out a little over 1 foot per day. A new sheet of Merv 8 daily would be most efficient

Despite your sarcasm, I'll respond in seriousness. The very Honeywell filters I'm talking about here, say they are rated for up to 12 months. And that is assuming you have it sized normally to the furnace. If you were to take a furnace that operates with a 16x20x1 filter and put in a 20x25x5 filter, you have increased the cross sectional area of the duct at the filtration point by over 50%, which means even a 1" filter would be operating with more than 50% more filtration surface area, plus the velocity through the filter would drop significantly, which reduces pressure drop even more than just the extra surface area. Then multiply that by almost 6 (using simplified assumption of same number of pleats - which to be fair is usually not the case) for the added thickness. So we're at about 9x there, without even factoring the reduction in air velocity, which is a substantial effect. I don't know how to do that math, but probably gets you up to about 12x with that factored in. Apply this to your original filter with anywhere from 1-3 month rated life, and annual doesn't seem so far fetched.

Compare to Honeywell saying their 16x20x5 model lasts up to 12 months (would assume ideal conditions, no pets, etc), and apply the more than 50% increase by going up to 20x25, and then apply the reduction in air velocity, and under reasonable conditions, it seems like 12 months is viable.

lkstdl said:

MTC, you are on the right track with the larger filter area. From the Energy Vanguard article The Path to Low Pressure Drop Across a High-MERV Filter:

Filter Area = 2.0 square feet (or more) for each 400 cfm of air flow.

You can also use return filter grilles, in which the filter lives at the start of the returns rather than in the plenum just before the furnace, making it easy to double or triple your filter area. Could be a good solution if there's not much space by the furnace. I haven't seen them in 4" depth though.

For the fan coils in our artist studios, we actually use 4 separate (in parallel) 20x20x4 MERV filters. The additional ducting and filter holders is a one time cost, and if it lets us run quieter and with less fan energy and more leeway as filters start to clog, in my mind its a good investment.

Thanks Luke, this is helpful. Got me down a rabbit trail of energy vanguard articles, once again. Been down that road many times, haha.

I struggle with their assertion that you just use the nominal area of the filter. I could maybe see this in terms of initial pressure drop, if that's your only concern, but it can't hold up like that for long. Surely that 1" and 4" thick filter that might not have a big initial pressure drop difference are going to be an entirely different story quite quickly. And I guess that's ok if you plan to replace monthly, but I'm not sure that many people are consistent about that. So I'd like to see the same comparision, somehow fairly done after a certain amount of loading, or after being exposed to exact same conditions for its rated lifespan, etc. This would probably need to be done in a controlled lab-like setting to get any accuracy. Then we could look at both of those numbers and get some sort of average pressure loading on the system. Going only on initial drop seems short sighted to me, particularly as someone interested more in low maintenance/longevity than in high performance filtration.

2 sq ft per ton (in AC terms) seems difficult for a normal home system. One of the properties I'm looking at doing this filter change on (the next one, so most focus on it right now), has a 2.5 ton AC. Its probably oversized, but the return ducting does not go to the 2nd floor, so the system has other problems to overcome... Using the 400cfm/ton estimate, that means I need 2.5 x 2sq ft, or 5 sq ft of nominal filter area. I could see that on a 1" filter, but seems excessive on a 5" (4 3/8" actual, based on the proposed Honeywell F100 media). In heating mode, the new furnace going in is 1200cfm max flow, so even worse. 6 sq ft of filter is hard to achieve at the furnace in most installations. And this isn't a big house...

This particular house has floor returns, so don't think filters there would work out well... too much junk falling on them, and it would look terrible through the return grills, if you could figure out a good way to mount them in there in the first place. Several of my other rentals also have floor returns - common in my area with lots of older homes that were usually later retrofitted with forced air.

I might consider converting my home ducted mini split to this, but I do have 4 returns in it, so not overly simple. One of them is also quite high, over a stairwell, so access would be challenging.

I do have another place in mind for this kind of upgrade in the near future, where it might be the best solution (one large, easily accessible return grill. I'll have to look more into filter grill options for that place. I was gearing up to redo the main return trunk to make room for an F100 or similar... this might be sufficient instead and easier, but not sure if there's enough depth to not restrict air flow in the process. I'll take a look next time I'm down there.

ChrisJ said:

pecmsg said:

The filter in your system is to protect the system, not replace the vacuum cleaner. 

If you do not want to change it monthly get a 5” media filter Properly installed in the return duct. 

My system actually has filter grills, with no filters in them.
I originally planned on two 12x12x1 filters, a 10x10x1 filter and a 14x30x1 filter. Some time during this, I realized the pressure drop across 1" filters and decided to shoehorn a AirBear 25x20x5 in by the air handler.

Sometimes the 20x25x5 filter lasts all summer. Sometimes it doesn't.
But, I have no doubt it was a better move than all of the smaller 1" filters as far as pressure drop. I also didn't like how the filter grills had openings all over where air would bypass the filter with no easy solution.

I'd be curious as to your actual results if you tried swapping to the 3) 1" filters. If it is indeed true that initial pressure drop isn't much different on a thicker filter than a thinner one, then in theory, you should have less drop with the like 25% greater surface area of the 3 filters. But they'd plug up faster and need to be replaced often, or the drop would quickly become worse.

The large amount of air gaps in the filter grills is an interesting point. They do seem to be a lot leakier than a good media filter at the furnace.

ChrisJ said:

MTC said:

ChrisJ said:

pecmsg said:

The filter in your system is to protect the system, not replace the vacuum cleaner. 

If you do not want to change it monthly get a 5” media filter Properly installed in the return duct. 

My system actually has filter grills, with no filters in them.
I originally planned on two 12x12x1 filters, a 10x10x1 filter and a 14x30x1 filter. Some time during this, I realized the pressure drop across 1" filters and decided to shoehorn a AirBear 25x20x5 in by the air handler.

Sometimes the 20x25x5 filter lasts all summer. Sometimes it doesn't.
But, I have no doubt it was a better move than all of the smaller 1" filters as far as pressure drop. I also didn't like how the filter grills had openings all over where air would bypass the filter with no easy solution.

I'd be curious as to your actual results if you tried swapping to the 3) 1" filters. If it is indeed true that initial pressure drop isn't much different on a thicker filter than a thinner one, then in theory, you should have less drop with the like 25% greater surface area of the 3 filters. But they'd plug up faster and need to be replaced often, or the drop would quickly become worse.

The large amount of air gaps in the filter grills is an interesting point. They do seem to be a lot leakier than a good media filter at the furnace.

If you look at an air bear filter and the housing they sell it has foam gaskets.
Each filter comes with new gaskets on two sides. The bottom I don't think has any as it just sits flush, but the lid has a beef foam gasket.

I'd expect a new 5" filter to have less drop than a new 1" filter as there's a lot more media to pass through because it's corrugated. If that's the proper term.....

I totally agree. I was referring to some of the info in the links provided above, that say that initial drop is actually not much different between similar filters of the same size, but different thicknesses. I find that hard to believe, but it is apparently true. I'd still opt for thicker for less maintenance... but if that is true, the 1" filters with about 25% greater nominal surface area should actually provide lower initial static drop. Doubt it would hold up long, and who wants to change 3 filters every month?

I'm considering the Honeywell, which might not be quite as air sealed, but still looks fairly tight. How did you end up picking the Air Bear?

Larry Weingarten said:

Hi @MTC , As you mentioned Energy Vanguard, how about writing Allison Bailes and asking for/suggesting a blog post on this topic? Share this thread. He's a very thorough researcher and sees things that others may miss. Then you can school all of us!

Yours, Larry

Not a bad idea. I might just have to do that.