There are numerous manufacturer's who swear these systems work and then you have the EPA who states this is not a regulated industry. It's buyer beware. In my opinion, any system which will help clean the air is better than nothing at all. It all comes with a cost.
Here's a white paper on UV light written by NADCA....
Here's a contractors explanation on video....
This link is not related to your question. It is worth watching so be careful what you recommend. You never know who's watching.
HVAC Scams; https://www.youtube.com/watch?v=TWbeNfVOKWo
Was there a catalyst? For disinfecting you are looking at UVC not UVA. I have seen systems that UVA activates a catalyst.
UVC is used in hospital operating rooms and have been shown to reduce the infection rate. UVc is effective at killing or damaging the DNA of viruses, bacteria etc. I think UVC can be beneficial in residential HVAC. There are not meant to disinfect the air but to reduce contamination loads to levels that the body can tolerate. I have seen bulbs that run at less than 40W.
You all may enjoy this "new" finding published on August 08,2014....
Formaldehyde can cause leukemia and at least two other types of cancer, the National Academies said in a review issued Aug. 8.
There is sufficient evidence from human studies to conclude that formaldehyde can cause nose and sinus cavity tumors as well as myeloid leukemia, the academies' National Research Council said.
I put them in my system thinking that the idea made sense. I turned them off after a year or so because (1) they wasted energy *and* because (2) I was convinced by experts on this forum or another that covers the same subjects that matters were even worse than wasted energy: they did not significantly improve IAQ, so they actually *squandered* energy.
If anyone can produce convincing scientific evidence that UV in the filter box is worth the cost I'd be interested to see it.
How do you measure what they prevent? For some people they can make a difference and others they may not see a noticeable diference.
I would not put one in a filter box. I would mount it above the coil. I think in some circumstances they would be beneficial and others not. It is hard to say. Depending on the unit they consume 36 to less than 100w. I would say if you have someone with asthma or other health issues or some type of sinus issue they could be of great benefit.
Air quality greatly affects the health of individuals. There are studies that show rates of autism are higher near freeways. Now UVC would not help that but overall in our homes and work places filters and UVC can make a difference.
As we make our homes tighter we need to think of the effect on indoor air. Ventilation is one way but filters are another way. I think you can add UVC to the mix. Also as the homes are tighter you will not fight the constant battle of air leak bringing in new pollutants. The filters will filter the same air more times making it cleaner. If you are using a UV light the same thing.
It is the finer stuff in the air that will give you the biggest problems. It is the small dust particles that you breathe in deeply, its the chemicals in the air its viruses and bacteria that get deep in your lungs. The more you can eliminate the better off you will be.
I agree with Robert 100%. To many people poo-poo away indoor IAQ. However, filters are only good for particulate collection which studies have shown will damage lung tissue. Living near a highway or industrial site or even in a home with new furnishings will emit chemical toxins into the homes air which filters will not help. UV from my understanding is designed to tackle certain virus and airborn pathogins. From what my research has shown me is that chemical emissions combined in modern building materials should be a red alert for many builders and homeowners. The problem for everyone is how to mitigate the problems with minimal expense. Seems the only cheap solution after Katrina is an installed HRV/ERV to help reduce these levels of toxins. Modern "green" studies have shown in low income projects the formaldehyde levels are unchanged between old versus new construction when these devices are installed. So what does this tell you? Now the real issue is testing for the unknown proprietary chemicals which are protected by law from disclosure. Is there a cheap solution? Doubtful. For now I guess we all have to continue hoping for the best and deal with cancer as we get it.
I put a watt meter on my unit at home with UV and ECM motor Ele air cleaner last yr was $210 ( with out tax and other charges) for both on 24/7/365. The ECM motor is on CIR so its some 450 FPM or 300 CFM or low low speed. til AC or heat is on then ramps up to make that speed that can take some 10 min to full speed. Using Air advice.com all VOC and dirt is way under the red mark.
Richard and Robert,
Good posts. You mention concern with chemical pollutants that aren't captured with particulate filters. My understanding is that UV lights can also create ions and charge particles in the airstream. How does ionization affect people? I'd say this is a legitimate concern with UV lights. But if lights are to be used certainly their greatest benefit is to illuminate the coil and not the filter.
Eric, not sure what you mean by "under the red mark". The downside of leaving the AH blower running continuous is that moisture left in the pan or on the coil when the compressor shuts off is reintroduced into the house. In my humid climate this is an issue.
Uv lights do not create any byproducts. You may be thinking about ozone. Ozone has some good uses in UNOCCUPIED buildings, Ozone will damage many things so regular use is not a good thing but if you have smoke or other odors you are trying to get rid of Ozone may be the ticket. Of course you need to remove living thing from the building. There are ozone generators and there are other things that produce ozone as a byproduct. Ozone is a by product in ionic cleaners such as the ionic breeze. What you should know is at low levels ozone doesnt clean surfaces etc as you will see advertised, it only does that at high levels. So if it is not going to clean at low levels and may potentially harm you why would you use it.
There are three things in the air. Particulates, gases, and living organisms. Filters work on particulates and larger living organism. Charcoal filters work on gases and uvc on the living stuff.
With furnace filters you want a mid level filter that is a balance between filtering and air flow. The best filters are very restrictive and should be used. The 4 inch filters you see are a merv 8-10 a mid range. They just have a lot of filter long life.
Austin air has a room air purifier that has a HEPA filter and over 7lbs of charcoal. The department is defense gave them to homeowners near the chemical depots when they were clearing them out,
IF you see words like super oxygenated etc those are buzzwords for ozone, They dont want to tell you that they pruduce ozone.
Here is a read on ionic air cleaners.
Air advice .com on there reports marks what in bad and red mark and higher is bad or above the EPA limit. I found the CO is lower than other ways and dirt to be higher than TSI and gray wolf. but over all a good start point of how dirty, high RH high/low temp, high VOC, high CO, high CO2 the building is.
If you seal the attic and seal the building the RH does not rise and good IAQ can be there. I find more return leaks than if the building is the return, you can not control the temp or RH if the building is not sealed
Respectfully speaking, RH does rise to the attic even in a sealed building. Heat rises and the moisture generated in the home by the occupants follows. Research is currently under way due to open cell spray foam odors in the attic and damp roof sheathing issues. Dr. Joe has described a ping-pong effect occurring with attic RH changes between surface temperature rise / fall from day to night.
GreenBuildingAdvisor.com wrote an interesting article about damp sheathing below;
"Increasingly, building scientists are investigating why OSB roof sheathing on many spray-foam-insulated roofs stays damp for months at a time. Most of these damp-sheathing problems involve open-cell foam rather than closed-cell foam."
Building Science Corporation describes the Stack Effect here;
Controlling RH can be achieved in any building sealed or not by use of a whole house dehumidifier or two or three. I personally have controlled the RH in my own home using 3 whole house dehumidifiers, but this comes with a significant cost. High RH also occurs with over-sized HVAC systems in old and modern homes.
To stay on topic here, many new homes have many more problems than RH. High TVOC is a modern problem which few have taken notice or even think it's a concern. "Real building scientist" are just starting to catch on to the problem. They are learning from blogs just like this and from people just like us. I'm not talking about those fancy wanna be building scientist with the alphabetical title aside their name. I'm talking about real scientist with real degrees from a real university. ;)
Heat does NOT rise! For heat transfer by conduction or radiation, heat transfers from hot to cold. For thermal transfer by convection, warm AIR rises because it is less dense than colder air- it is all relative. If you have leaks to the attic, warm air will leak to the attic and pull colder air from any gaps in the exterior below. That is the "chimney" or "stack" effect.
If a house is well sealed and insulated, there will be little temperature difference between low and high and thus little convective air movement.