Wow Jim, A thoughtful and detailed response that I fear I don't have the info at hand to do justice to. I was indeed referring to the "mid-summer" compared to "mid-winter" differential, not to variations within those seasons. The homes I'm thinking of include a range of quality of construction (I'm guessing) but not at all cheap or mass-produced. Probably built from mid-50's thru 60's. I think they all must be (as you call it) slab-on-grade, because that's one way I recognize them! Then when I don't see any other obvious source of heating, I mentally prepare for the worst. I get your point about the more outside air coming in during winter, the drier it will be indoors, and the importance of a slab vapor barrier, etc. I'm sure these houses didn't have the benefit of the kind of integrated approach that you applied in your home (although the "worst" one was designed and built by its owner, an academic engineer and professional architect!) I'm assuming that, given a learning curve from past disasters, in-floor heating is now a far more domesticated animal. You've already drawn a decent picture of the kinds of variables involved and the potential for unfortunate unintended consequences. If I grasp it correctly then these interiors could be particularly harsh climates if certain factors were not accounted for. Say more if you wish – I for one find it very interesting and others must as well . . . Thanks, Joseph On Dec 12, 2012, at 12:58 PM, Ron Nossaman wrote: > On 12/12/2012 9:39 AM, jim ialeggio wrote: >> Ron, could I ask you to forward this to the list for me? I'd like to >> leave the title as above without adding FWD prefix, so it stays within >> the thread. I'm interested in this thread, and several of my posts don't >> seem to be getting through since yesterday eve. I have an email in to >> the list admin. >> jim >> >> Joseph Giandalone wrote: >> >> <Now, Why is it that in my long term observation here in mid-New >> England, pianos in underfloor-heated homes have the most extreme >> symptoms of seasonal humidity variation? >> >> Ok...Lets get some info. How old are these ranch houses? How drafty are >> they, ie how much exterior air is brought in, heated, then "exhaled", as >> new cold, bone dry NE air is brought in? Are the homes older >> inexpensive construction? Your observations seem to be targeting a >> particular subset of home construction, slab-on-grade. So I'd like to >> confirm the specifics of what the moisture sources are before drawing >> any large brush conclusions. >> >> In addition, your post refers to seasonal fluctuation. So I'd like to >> focus on that. Would you specify what you mean by this. To me "seasonal >> fluctuation" means a 1 time change at the beginning or end of the >> heating season. Is that what you mean, or do you mean instability during >> the entire heating season? >> >> Most of the slab-on-grade ranches in MA that I am familiar with are >> bottom of the line entry homes, with older, inexpensive construction. >> These slab-on-grade homes are generally older, cheap construction, with >> no moisture barrier between grade and slab, and no insulation at the >> perimeter of the slab. A slab with no moisture barrier is very often >> creating a very moist slab in summer. This slab adds a huge amount of >> moisture to the building interior during the summer, AC or not, even if >> there is no apparent wetness on the slab. The most recent building codes >> are very picky about slab insulation and moisture barriers these days, >> so I would differentiate between older and newer construction. >> >> Moist summer slab conditions, in addition to normal summer high RH%, >> means the swing to heating season has to first cook out that moisture >> from the slab. That cooked moisture has to go somewhere, and the >> interior of the home presents the path of least resistance...so it goes >> to the interior. This most likely creates an RH spike at the beginning >> of the heat season, followed by a significant RH decrease while the slab >> is in heating mode. In addition, in a drafty building, the decrease in >> RH will continue to aggressively drop of a high air change rate. >> >> So are you referring to a single fluctuation at the beinning and/or end >> of the heating season, on general instability during the heating season? >> >> Jim Ialeggio >> >> Jim Ialeggio >> jim at grandpianosolutions.com >> 978 425-9026 >> Shirley Center, MA >> >> >> >> >
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