Monday, April 12, 2010


Last week on Wed. we had a meeting with Forrest, our architect, to discuss the geothermal design contract. The contract had a lot of assumptions about our situation that weren't true, but Forrest said that his experience with the company was generally good, except for the design contracts. They tended to do this - put lots of irrelevant stuff in the contract - just to make it look more precise, though, actually, since it didn't correspond to our situation, it made the contract look inaccurate. We decided to take his word for it and go ahead with the design.

Later in the meeting, we reviewed a list of items that I have been accumulating. One of them involved soundproofing the geothermal heat pump and HRV system to ensure that they do not generate a lot of noise. Forrest told us that the HRV systems were, in fact, noisy but that there were measures, such as bending the pipe 90 degrees at the vent, to reduce propagation of noise from the HRV unit to the vent, although sometimes this couldn't be done. HRVs are mechanical ventilation and anybody who works in an office building knows what that sounds like. Basically you are working with the sound of a fan running in the ceiling all day as the accompaniment to your creative thoughts. Forced air heating sounds the same way.

Our house is particularly susceptible to noise, since it was built in the 1970's and there is nothing put into the structure to inhibit vibrations from one part of the house - say, the running fridge in the kitchen downstairs - from propagating to another - say, my office upstairs. When we had radiant heat put in a few years ago, we were astounded how quiet the house became in winter. It's not that you can't hear anything, the furnace still makes a low frying noise from the burning gas, it is just much quieter than having a squirrel cage blower whaling away in the mechanical closet, and the sound of the air whooshing out the vents. There's also the almost inaudible sound of the solar hot water pumps usually in the afternoon of sunny days, and, of course the fridge. But all these add up to very little noise, and the noise is also intermittent. With tightly insulated houses, the HRV system must be on all the time, otherwise the air quality inside the house suffers.

I found this a little hard to understand, since the German Passivhaus standard requires HRV. Passivhaueser (in German, "passive houses") are basically so tightly insulated that they require no supplemental heating beyond that from the appliances (like the fridge) and people within them, even in the cold German winters. An HRV system takes fresh and possibly cold air from outside, circulates it through a heat exchanger with stale air from inside on the other side of the heat exchanger, and exhausts the fresh air into the house and the stale air to outside. In this way, the occupants get fresh air but the heat is retained. Our insulation would not be that tight, since we have the solarium on the back that probably leaks heat and air, and also, we are not reinsulating the master suite nor one wall in the kitchen, but nevertheless, the amount of insulation we are putting in is enough that it could cut down on the amount of air infiltration sufficiently to allow air quality to suffer. We already have a problem with cooking odors lingering into the next day.

Now Germans are particular about noise in their houses. Even regular German houses are very solidly built in comparison to American houses, usually from ceramic bricks shaped like cement blocks, and they have heating systems that run on oil or gas that either use radiant heat as we do or radiators under windows. American houses are flimsy in comparison. All this mass makes for a very quiet house indeed, very little traffic noise penetrates. So I found it hard to believe that HRV systems could be noisy, the Germans who are now building lots of Passivhaueser, would never stand for it.

Naturally, I went on line to try to figure out what the problem was. In particular, I wanted to find out how much noise HRV systems emitted. The specs for the unit Forrest recommended had no noise rating. But - surprise! - the same thing was true of every single unit manufactured in the US or Canada that I looked at (and I checked 10)! The only unit sold it the US that had a noise rating was the Panasonic WhisperQuiet(tm), which is made in Japan. The WhisperQuiet is actually a bathroom ventilator, because it exhausts directly out of the unit rather than through a duct, so it is unsuitable for our situation, but the noise rating (though in an unusual measurement) was quite good.

Even more surprisingly, every single unit manufactured in Germany and sold in the other countries of the EU had a noise rating on it! The quietest I found were products manufactured by Paul Lueftung. There are various models, but the noise rating ran from 18 db to around 33 db. This is about the amount of noise in a quiet room, and these units are in fact used in Passivhaueser. Products from other companies typically started at 35 db. Unfortunately, the units conform to the European power standard - 230V/50Hz. In the US, we can get 220V which is probably OK, but 60Hz which might be a problem for an AC motor. The units may have DC motors and a power supply, in which case, we could convert them to our power standard. I need to look into this as a possibility.

It seems rather strange that the US manufactured products don't come with a noise rating. Don't Americans care about noise? I guess not since they put up with noisy forced air heating and noisy ventilation in offices, or maybe the sound of all that electricity being used makes people feel like Progress is happening. But I suspect the answer is much simpler: the German government requires manufacturers to include noise in their technical specs whereas the American government doesn't. Guv'ment regulation! The German technical specifications were also considerably more complete and prominently available on the manufacturer's web sites. In several cases, it was difficult to find the American manufacturer's specs, and they were quite skimpy, for example, the noise rating was listed as "quiet".  Of course, your "quiet" might be my "noisy", a db rating is much more objective.

I also looked briefly into noise from geothermal heat pumps, there the situation was the same. Lots of web sites talked about how little noise they generated outside, in comparison to air source heat pumps, but nothing about the actual noise generated by the heat pump itself. I figure that there are three components to noise from the heat pump: the pump circulating the heat transfer fluid into the ground and out, the compressor, and the forced air system (if the system is forced air). On heat mode, our system won't have the latter since we use radiant heat, but we would have the first two. On air conditioning mode, of course, we would have to put up with all three, but there is nothing we can do about that, it is not possible to use a radiant heat system for cooling. I figure that the compressor can't be much noisier than a fridge and the heat transfer fluid pump should be about the same as the solar hot water pumps, but then who knows? A fridge we got in our old house was so noisy that we got rid of it after a couple years, we could not afford to do that with a heat pump. The heat pump will probably have to be American manufactured because the electrical system is probably too complicated to convert,  so it could be bad.

Anyway, we asked Forrest to hold off on the geothermal design and the HRV design until we get more clarity about this issue. In the worst case (i.e. we can't get a quiet HRV system), we can back off the insulation and  just do under the floor (where the current fiberglass batting causes lots of radiant heat to leak in to the crawlspace) and on the central hallway ceiling, which must be replaced due to cracking, then we probably don't need HRV.  As for the geothermal,  maybe we could mount the compressor and heat transfer loop pump in the garage, and the heat exchanger in the mechanical closet. Or possibly get some kind of soundproofing under the compressor so it doesn't shake the floor.

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