nancy_pnwzone8(OR zone 8) ps here are some links if you're interested. Wolverton Environmental Services http://www.wolvertonenvironmental.com/ Plant Air Purifier http://www.plantairpurifier.com/ Andrea http://www.andreaair.com/ Inside Urban Green - What did Bill Really Say? http://www.insideurbangreen.org/2009/11/my-entry-1.html Phytophilter Technologies http://www.phytofilter.com/ Plants are the Strangest People - Indoor Plants as Air Purifiers http://plantsarethestrangestpeople.blogspot.com/2008/04/indoor-plants-as-air-purifiers.html Kamal Meattle: How to grow fresh air http://www.youtube.com/watch?v=gmn7tjSNyAA (i would be remiss for posting this link without providing more info. in this TED talk, it sounds like they just added some plants to a big office building, like you would see in a typical cubicle farm, and - shebang - the air was cleaned. what he doesn't show is that they have a full on indoor grow op with high intensity lighting and full hydroponic plumbing. the grow rooms are tied into the building's HVAC. there was another video that showed the set up but i can't find it now.) I would add these links: 1. Wikipedia Houseplants together with the medium in which they are grown can reduce components of indoor air pollution, particularly volatile organic compounds (VOC) such as benzene, toluene, and xylene. Plants remove CO2 and release oxygen and water, although the quantitative impact for house plants is small. Most of the effect is attributed to the growing medium alone, but even this effect has finite limits associated with the type and quantity of medium and the flow of air through the medium.[25] The effect of house plants on VOC concentrations was investigated in one study, done in a static chamber, by NASA for possible use in space colonies.[26] The results showed that the removal of the challenge chemicals was roughly equivalent to that provided by the ventilation that occurred in a very energy efficient dwelling with a very low ventilation rate, an air exchange rate of about 1/10 per hour. Therefore, air leakage in most homes, and in non-residential buildings too, will generally remove the chemicals faster than the researchers reported for the plants tested by NASA. The most effective household plants reportedly included aloe vera, English ivy, and Boston fern for removing chemicals and biological compounds. Plants also appear to reduce airborne microbes, molds, and increase humidity.[27] However, the increased humidity can itself lead to increased levels of mold and even VOCs.[28] When CO2 concentrations are elevated indoors relative to outdoor concentrations, it is only an indicator that ventilation is inadequate to remove metabolic products associated with human occupancy. Plants require CO2 to grow and release oxygen when they consume CO2. A study published in the journal Environmental Science & Technology considered uptake rates of ketones and aldehydes by the peace lily (Spathiphyllum clevelandii) and golden pothos (Epipremnum aureum.) Akira Tani and C. Nicholas Hewitt found "Longer-term fumigation results revealed that the total uptake amounts were 30−100 times as much as the amounts dissolved in the leaf, suggesting that volatile organic carbons are metabolized in the leaf and/or translocated through the petiole."[29] It is worth noting the researchers sealed the plants in Teflon bags. "No VOC loss was detected from the bag when the plants were absent. However, when the plants were in the bag, the levels of aldehydes and ketones both decreased slowly but continuously, indicating removal by the plants".[30] Studies done in sealed bags do not faithfully reproduce the conditions in the indoor environments of interest. Dynamic conditions with outdoor air ventilation and the processes related to the surfaces of the building itself and its contents as well as the occupants need to be studied. While results do indicate house plants may be effective at removing some VOCs from air supplies, a review of studies between 1989 and 2006 on the performance of houseplants as air cleaners, presented at the Healthy Buildings 2009 conference in Syracuse, NY, concluded "...indoor plants have little, if any, benefit for removing indoor air of VOC in residential and commercial buildings."[31] Since high humidity is associated with increased mold growth, allergic responses, and respiratory responses, the presence of additional moisture from houseplants may not be desirable in all indoor settings.[32] sourse: https://en.wikipedia.org/wiki/Indoor_air_quality#Effect_of_indoor_plants 2.Critical Review: How Well Do House Plants Perform as Indoor Air Cleaners? Dingle et al. (2000) reported on a field study of three portable office buildings in Perth, Australia to test removal of formaldehyde by plants. Five plants (five species) were added to each room every two days to a maximum of 20 plants (at 2.44 plants per m2) after nine days. Two adjacent portable office buildings were used as controls with no plants. The mean formaldehyde concentrations were about 850 ppb, except with 20 plants. The authors state that the results show “no change in formaldehyde concentrations with the addition of 5 or 10 plants in the rooms and only an 11% reduction in formaldehyde concentrations with 20 plants in the room.” They did not indicate that this reduction was statistically significant.... With this caveat firmly in mind, it is hardly surprising that the HBI study failed to find any effect on pollutant removal by plants, despite a reasonably strong study design in terms of using controls. The study by Dingle et al. found only an 11% reduction in formaldehyde with the highest loading of plants (20 plants in a room or a loading of 2.44 plants per m2), which is not feasible in the real world and is probably not statistically significant. ... Sourse: http://www.buildingecology.com/articles/critical-review-how-well-do-house-plants-perform-as-indoor-air-cleaners/ I think people overestimate the ability of plants to clean the air. That's why EPA don't write about plants as cleaner at all: Epa wrote about Mechanical air filters, Electronic air cleaners, Gas-phase air filters, UVGI cleaners , PCO cleaners, Ozone generators , Portable air cleaners but EPA don't write about plants as cleaner at all.Sourse: http://www.epa.gov/iedweb00/pubs/residair.html If you use plants as cleaner You need to test air inside your house or flats. You need to use complex devices to test air otherwise you may find that you don't have any benefit from plants at all. And this is only placebo. You can spend your time for nothing. Only complex devices to test air inside your houses or flats can help you. Please don't trust so much NASA or Wolverton. Be critical. To read Critical Reviews too. Сheck the air in your homes with complex devices.

My advice is drop the "ROI" requirement. It is essentially useless. Historically, anything with a payback period greater than 9 years has a negative financial impact. Currently, anything with a pay back period greater than 4 years has a negative financial impact, but I wouldn't use the 4 years to make a financial decision, additionally, mortgage money is essentially free right now. The unfortunate problem with any "efficiency" is that rarely do they make financial sense. Even spray foam insulation has a bad ROI. I am not saying, don't do these things. I am saying take a different look at these things. Do away with the whole "ROI" requirement and just look at the price for items that are going to make you more comfortable. If the price seems too high for the enjoyment and benefit you are going to get from it then scrap it. Now some finance stuff that is probably too much like being back in school and way above what you asked so you might want to just stop here. ROI = (gain from an investment - cost of investment)/cost of investment. This will always return a percentage. The percentage is then compared against other investments. What you have been talking about is not an ROI but a payback period. Which is not a big deal but understand that companies don't use payback period to make financial decisions because it doesn't consider the time value of money. Put simply a dollar today is worth more than a dollar in 10 years. The reasoning is that you could put the dollar in the bank and grow it. The tool most often used by sophisticated companies to make investment decisions is Net Present Value. You can jump on Youtube and look it up if you want but an easier way to think about it is just to use a Present Value of an Annuity Calculator, the one here at Investopedia is easy to use. In the top box (interest per time period) enter 5 if you are very conservative and 9.84 if you are fairly aggressive, or anything in between (5% is historical T-bond and is essentially risk free and 9.84% is Stock market since the crash.) In the second box enter the amount of time you plan on having these savings, and in the third enter the amount you expect to save annually. If that amount is more than you are paying today it is a good investment. If it is less then it is not a good investment. This is still a rough calculation to get a good calculation you will have to use a Net Present Value calculator. Sorry it is so long, I hope it helps.

" It is a very hard design to heat or cool evenly." That is undouptedly true and all the more reason not to mess around with diy, roll your own and home made desighn changes to hvac system. On the surface your idea sound's like there is a free lunch to be had pulling cool air from basement. It's far more complicated than sticking a return in the basement. For every cubic foot of air sucked from basement,another cubic foot must replace it. That make up air can only come from outdoors (a terrible idea) or withing the building(which is exactly how every room in building is usually desighned). Trade schools spend hours teaching techs this so just believe me when I tell you for every cubic foot of air "falling down stairs"another cubic foot already "falls right back up them". So if you want to heat and cool basement,you should have ducts in it. If you don't care to have basement heated and cooled,make certain there are no leaks in existing ducts ( both supply and return ). Now so you don't go away empty handed,a simple test that might tell you if theres a leak in supply or return in basement. Hang a bed sheet,thin plastic or similar light fabric to cover doorway leading to basement. If sheet moves toward basement there's a leak in return. If sheet moves away from basement there's a leak in supply. If sheet doesn't move at all the bad news is there's a "REMOTE" chance leaks of exact same size exist's in both supply and return. I'm assuming your air handeler is in basement or main trunks run through it,if not,little I've said is applicial for your house.

What Hallett & CO suggested, that's the place to go. Ordered a few custom grills from there, they do make nice stuff. Just make sure you specify Material-Steel Design-Metal and that it will be used a floor return grill.