[pianotech] Protection from underfloor heating

[Ron Nossaman]

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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