An essential part of the discussion centres around absolute humidity (AH) and relative humidity (RH) of air.
I know for instance (through having kept an eye on my combined hygrometer and temperature gauge over the years) that RH in the houses I’ve lived in in the UK generally hovers somewhere between about 35% RH on the low end to about 60% RH at the top end. The higher RH values tend to occur in the summer incidentally.
Has anyone undertaken the exercise I’ve described and is willing to share their data with me? As I’m based in the UK and drawing data mostly from UK sources then ideally it would be UK numbers I’d use. However, if someone has compiled such numbers elsewhere in the world I could still use them. Any chart created would simply need a note giving the geographical location of the data source.
The raw data would be fine as I can crunch the numbers and create the chart simply enough. I would credit the source of the data in the manuscript.
Replies
Richard, I do not have such data, but this would be an excellent time to start collecting, and over a period of 3-4 months, I'd have pretty much the entire swing we experience here in the Great Northwest.
We are on the 2nd day of a heat-wave after a long period of pretty dry weather, so the next few days will probably be the absolute driest of the year. We'll have showers here and there through Sept., and then the rain will start. By the end of October, or certainly mid- to late November, it should be about as "moist" as it can get.
So, if it would be any help, I'd be glad to keep a chart for you.
PS: Although I heat the shop during the winter months, I'd likely not start heating before mid-November.
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Edited 7/22/2006 3:58 pm by forestgirl
I'm pretty sure Hoadley has a graph showing these data. The other likely source would be the Forest Products Laboratory. Most of their research is available on-line.
Richard wrote "...but I've never kept a daily record of RH changes inside my house or workshop." My copy of Hoadley is at home (I'm at work now). Questions: (a) Why would he have included shop RH info in his book and (b) If he did (I'm doubtful) how many different geographical locations would he have included?forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
He didn't FG. There's useful information in his book, but it's not exactly what I was after. See my reply to Steve for further explanation. Slainte.Richard Jones Furniture
Ah, the FPL source is a good idea, Steve. I'd forgotten to try them.
Hoadley doesn't really have the information I'm after. In the end it's not absolutely essential, but would be useful. I can get by without it it for now.
Actually, part of what I'm trying to do is create something that presents timber technology information in ways more accessible for the woodworker than Hoadley does. Hoadley is a mine of information, but you have to be able to read dense inpenetrable text, which I can.
Lots of woodworkers, e.g., my learners that I have to deliver timber technology to have things like dyslexia and other learning difficulties and find graphics and other visuals easier to learn from. Dyslexics tend to be do'ers not readers, hence their interest in arts, crafts, etc.. So if I can find a way of presenting information in both words and graphics I'll think I've succeeded quite well.
I might be able to sell the verbal spew I come up with for money too, ha, ha. Slainte.Richard Jones Furniture
FG, to get a true picture you need to collect data over 12 months. Take readings of temp and RH twice daily at the same time each day, e.g., 7 am and 4 pm or something else convenient. This way you'll be able to create a chart showing the average daily RH and temp for each month over a 12 month period.
If you wanted to get really analytical and closer to scientific you could also cut up a plank of wood that's exactly something convenient, e.g., 10", 20" or 30" wide and measure the width precisely each day over the year. If you had two or three bits of wood like this, you could put one in your house, one outside on the porch sheltered from rain, and one in your workshop. Of course, you'd need a hygrometer/thermometer located near each piece of wood and record all the data daily. That's all getting a bit too onerous really, but if you had a passion for knowing that kind of information you could do it, ha, ha--- ha, ha.
In your area, PNW Washington coast, average minimum January internal RH is usually about 55%, and average internal wood furniture MC is ~10%. It depends a bit on your heating and insulation, etc..
Average minimum July internal RH is about 70% and average wood furniture MC is about 13% MC.
Go just a few miles east from where you are and over the mountains to the high savannah and you can knock off 3-4% from the January and July wood MC figures I gave you above.
Your offer of help is very kind but, like me, your data recording would take a year to produce results. I expect results early next July. Slainte.Richard Jones Furniture
Best of luck finding someone who has these detailed records. I hear ya about going over the Cascades. My husband works in Eastern OR and is currently living in Easter WA. It's brutal over there -- hot, dry, unbearable IMHO.
For data collected over a full year, seems like so much would depend on the personal habits of the collector -- most especially, how much they use their heat (or air conditioning), and what kind of heating they have.
"Average minimum July internal RH is about 70% and average wood furniture MC is about 13% MC." Internal RH seems rather high. Precipitation in July averages .93 in., the lowest of the year. In June it's 1.55 in.
For those who think they might want to live here (LOL!) here are the graphs on temp, rain and sunshine.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
"Internal RH seems rather high"
I'm not sure FG, but I did get that information out of Hoadley, p 134, although there does seem to be a typo or error in his charts there that I noticed several years ago. It leads to some uncertainty about the data he's presenting. Slainte.Richard Jones Furniture
Ah, now I'm home, Hoadley in hand. I see where the confusion lies about my particular geographical area. You have meet situated in the "PNW Washington coast." Nope, I'm on an island in the Puget Sound, 9 miles west of Seattle. The lines that go through us on page 134 indicate 50% RH and 10% furniture MC. Whew.
We're the little orange dot that says "Winslow" which was the old name for the downtown area. As you can see, there quite a bit of the state between us and the coastal area of Washington (The Olympic Peninsula mostly).
View Imageforestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
For an example of what I'm doing, FG attached is a graph I created of average external RH and temperature per month for London, UK. I'd like to do a similar graph for internal RH and temperature, but I don't have the data to hand.
I can get by without it, but it would be nice to have. Slainte.
Richard Jones Furniture
Edited 7/22/2006 5:09 pm by SgianDubh
Hi Richard,
In coastal NSW, we aim at 12.6% being aim EMC to average summer and winter swings.
It's really the reverse of the US situation here, where our winters are damp and humid (so you get timber swelling) and the hot, dry or hot, humid summers tend to cause timber shrinkage.
With the recent trend (about 15 years ago) to air condition most homes, the common scenario is changing now to maintain timber in a dry atmosphere that the a/c produces.
For what it's worth, I can remember being told that timber moisture content in (unairconditioned) homes is between 8 and 14 percent in the timber, but that's not really the scientific data you're looking for.
Thinking through it, I don't think that you'll get a 'norm' here as the house heating has too much influence on internal conditions to give a meaningful 'average' that the punter on the street could use as a guide. You could mention that 'bone dry' timber has usually (correct me if I'm wrong) 6-8% moisture and that it is usually received from the timber yard at 4% approx above local EMC, as this minimises their kiln drying costs.
I ran a quick google search and found this info that may be of use (some of these, alot more than others)
http://www.ces.ncsu.edu/nreos/wood/wpn/valueadd.htmhttp://www.timber.net.au/documents/FWPRDC_Flooring_Manual.pdf (the google summary indicated that this had your information, but I'm on dialup and it's 60pp long so I didn't wait to browse it in detail.)http://www.englishtimbers.co.uk/tech/siteconditions.html#climate (this could be what you're looking for.)http://www.woodweb.com/knowledge_base/Indoor_Wood_Shrinkage_and_Expansion.html
Here's the searches I used:
Search 1Search 2Anyway, I have to run as it's 8am sunday here and it's family time this morning.
Cheers,
eddie
edit: more data:http://sres.anu.edu.au/associated/fpt/drying/intro.html (uni website on timber EMC)http://sres.anu.edu.au/associated/fpt/drying/drying.html
http://www.timber.org.au/Resources/DS2%20Pre-Installation%20Assessment%20Oct%202005.pdf (this has what you're looking for.)
http://www.ces.purdue.edu/extmedia/FNR/FNR-131.html
Edited 7/22/2006 5:45 pm by eddiefromAustralia
Thanks for those links Eddie. Unlike yourself, it's late Sat pm here and I'm about to go off to my pit and snore a bit. I'll check those links tomorrow.
I take your point on the kiln drying. Here in the UK kiln operators aim to dry furniture grade wood to 10% MC. There's little point kilning any lower really because in service in most UK houses furniture hovers between about 8% and 12%. There are exceptions either side of those numbers.
When I lived in Texas all the American kiln operators reckoned they were drying wood to numbers like 6% MC. A total bloody waste of time and money for my area because in Houston by the time I bought their 6% KD'd cherry it was at a minimum of 10% MC and usually 12 or 13% MC, and rising rapidly too.
Of course once the furniture was made and installed in Houston houses it'd start losing moisture again and end up swinging about between about 9%+ in the winter and up to 14% in the summer. Slainte.Richard Jones Furniture
Sgain
Looking at those temps, no wonder we had so many volunteer as immigrants 200 years ago (and they're still comming)
dave
You're right there, Patto. The courts up here 'volunteered' plenty of immigrants to Oz, ha, ha-- ha, ha, ha.
Good point about the museums and the like though. It might be worth contacting a few to see if they have some numbers. Slainte.
Richard Jones Furniture
Edited 7/26/2006 10:34 pm by SgianDubh
Wouldn't such information be collected by the weather services? I went to the site for the United States' NOAA (National Oceanica & Atmospheric Administration), and at this page page see links to lots of historical data. Maybe some of this would be sufficient for you, or you could find something similar in the UK that would be more applicable for your target audience.
John, I haven't found a weather service site that's conducted a survey on the RH inside a habitable building. I know that people other than myself have observed RH numbers inside buildings, but how carefully they've logged and tabulated the numbers is another matter.
I've casually kept an eye on combined thermometers/ hygrometers inside workshops and houses I've worked and lived in over many years. From these sporadic, casual observations I'm aware of the RH range I expect houses to experience-- basically the internal RH inside most British houses swings between about 40% in the winter and 60% in the summer. There are variations either side of those numbers due to particular circumstances.
I've simply never kept a record on a daily basis to compile a chart. I wondered if anyone else had.
On a side note there are published guidelines for wood moisture content suitable for various internal and external uses, e.g., British Standard, BS, EN 942 1996 Class J30. You can work backwards from this information to establish roughly what sort RH range the wood is intended for.
Incidentally, and perhaps surprisingly to some readers here, that 40-60% RH range is also roughly what I found my house in Houston, Texas experienced too.
But, many thanks for the link. I certainly found interesting information there. Slainte.Richard Jones Furniture
Richard
I found a chart of the mean monthly EMC of Monterey Pine (Pinus radiata) under sheltered outdoor conditions throughout the year in 7 major Australian centres. Whilst the location is probably of little relevence the chart is at least interesting.
I can email you a copy if it's any use.
Don
Don, I'd really like to see that information. I can glean a lot from that sort of thing, even though as you say, it relates to Oz conditions. Many thanks for the offer.
If it's a Word document it could certainly be emailed as an attachment, as can other formats. Rather than publicly put up my email address (always been reluctant to do that) would you mind clicking on my website link just below and going to the contact button there to get it?
Many thanks. Slainte.Richard Jones Furniture
Richard
Its from a text I had when I did Timber Technology back in the early '90s (remember then - when every thing was printed:-) . I'll scan it & send it to you.
Don
Richard,
Not a habitable house, but many museums and gallerys keep accurate temp and humidity records. Given the propensity towards airc/heating in houses these days, such records are probably closer to reality than they once might have been (particularly for people who can afford custom solid furiture).
dave
Richard,
I don't know how much this will help. I moved from Hawaii to Arizona this time last year. I flew back and forth several times before the move, experiencing severe "dry eye syndrome" as result of the very dry air in airlpane cabins. I became a little obsessed by the situation and bought a Radio Shack digital hygrometer/thermoneter and carried it with me on several flights to see how dry the cabin was.
The unit "bottomed out" at 20% RH. I continued to carry it around with me for months, first monitoring my house in Hawaii, many times a day -the range inside my house and the shop was 55% (the lowest I ever recorded there) to 89%.
When I moved here to Arizona, I stayed fascinated with the subject. I arrived at the end of the "Monsoon Season." The hygrometer NEVER measured higher than its low end indication (20%) from mid August through last March. I checked it many times every day. Often, the weather service reported ambient RH of 5-10%. During the winter, with the heat on in the house, the internal RH was obvioulsy lower than that.
We are back in the Monsoon season now (have been since mid -June, early this year). It feels much more humid than Hawaii ever did, but my hygrometer broke months ago. I'm going to get a new one, and I might have some end-of-monsoon season readings before Arizona drops back down to its typically arid conditions.
Rich
Rich, that's very useful information. It confirms what I already knew of the Arizona region. It has similar weather patterns to parts of Australia, Africa, the Indian sub-continent and other areas that fall roughly in a latitude band between 25º and 35º.
Presumably you're running what I've heard called 'swamp coolers' to add moisture to your house? Slainte.Richard Jones Furniture
there are places in the world that get more than 15" of rain?
Yeah Patto. Near Houston one year- June 2000 I think, some place in Montgomery County just NE of Houston itself got ~44" of rain in five or seven days. Enough to float a boat on anyway, ha, ha. Slainte.Richard Jones Furniture
Richard,We don't have a swamp cooler, though many in the area do. We have standard air conditioning.I guess a swamp cooler is of double benefit when it is very hot AND very dry, but they must be pretty useless during hot and humid conditions. I guess they could serve as humidifiers when it is dry and cool, but not yet cold (it goes down to 10 F in winter).Rich
Rich, my understanding is that swamp coolers wouldn't help much in hot humid conditions.
But I think they help quite a bit in very dry atmospheres where they add moisture to the air thus reducing the dehydrating effect. I'm pretty sure they were fairly common in places like Arizona, but perhaps moreso in workshops than in houses. I'll have to check that out.
Thanks again for your information. Slainte.Richard Jones Furniture
If you are looking for more widely distributed geographic information on humidity, musicians might be a group to ask. There are a lot of them, string instruments are rather sensitive, and they travel at all times of year.
Alan, I'd not thought about musicians and how humidity affects their instruments, but you make a valid and interesting point.
I've managed to find all the information I need on relative humidity. I've been able to look at data relating to several geographical regions and climate types. It makes for informative study.
However I've decided in my manuscript to use UK based data. That's UK external AH, RH and seasonal temperatures along with typical RH and temperatures from UK habitable buildings. I think it makes the text logical because I discuss in some detail conditions that apply to one geographical location. I then go on to discuss in less detail other conditions that woodworkers work in, such as Houston, a city that I have experience of.
The intention is that readers will have enough information that they can make informed decisions for their own circumstances. Thanks for the pointer. Slainte. Richard Jones Furniture
Richard, I did some googling and happened upon http://www.jbest.net/weather/weatherSearch.aspx, which appears to have daily weather statistics for Colchester, including high, low, and average indoor RH, from 29/1/2004 to the present.
Getting the daily statistics from the web site would be doable, but tedious. They seem like nice people, though, and if you left them a message at http://www.jbest.net/contactus/ and explained what you're doing they might be able to break out the data for you in a more useable form. Seems worth a try, anyway. Slainte, Dan
Once again Dan you come over the hill like the cavalry to my rescue! The website you pointed me to has just the information I was looking for.
With a very small amount of work on my part I can create a graph (of typical residential RH figures over a year) that will illustrate the text. It's a residence in the UK of course, but that ties in rather well with outside RH figures for London-- the chart I included as a click-on earlier in this thread.
I've already extracted the relevant RH numbers from the website. Now I need to email the couple that put these numbers together and seek permission to use them in my manuscript.
Incidentally, I dropped you an email via Taunton's emailing facility after your last help. I offered to send you an extract of a draft of my manuscript relevant to atmospheric RH, AH and its effect on wood. It was intended as a token of my thanks for your help. Did you get it? Slainte. Richard Jones Furniture
Richard, received your email and replied to it the same day. Maybe the reply got mixed in with some spam? I'll send another right after I post this. Just in case that also goes astray, the answer was yes, thanks, certainly I'd be interested to see it. Slainte, Dan
Here in your erstwhile God forsaken hometown, Richard, the humidity is always realtive, inside and out.
It is simply high.. or too high.
But you already knew that, eh?
Let me know when you're planning to pay us a visit. I'll buy 'ye a pint or two!
Bill
Bill, nice to see your name again after all this time. How is Houston? Don't answer. I already know. At this time of year it's always ten hot. That's five times hotter than too hot, ha, ha-- ha, ha, ha.
I don't know when next I'll be in town, but I'll aim to avoid the summer months-- I always think December and January are Houston's best months for weather.
But when next I do visit I'll get in touch for that beer. Slainte.Richard Jones Furniture
Great, Richard. Looking forward to hearing from you. And I wouldn't come here myself unless it were in the winter.. such as winter is here.
It's 'nigh midnight in your part of the world right now. Time to tuck in and thank your lucky stars you're not in Houston.
I just wanted to say thanks to all for your time, suggestions and efforts to help. I found what I was looking for with the help.
The data has been turned into a graph and the text accompanying the visuals is moving forward.
Onwards and upwards, or something like that. Slainte.Richard Jones Furniture
I would question your basic premise, which would seem to be that knowing the relative humidity inside of a specific building is useful information for designing and building a piece of furniture.
I suppose it might be relevant if the piece were a built in, but for any other furniture, I always presume that it could end up anywhere in the world, or be stored in a damp basement or overheated attic at some point in its (hopefully) long life and that I'm obligated to build the piece to handle the extremes, which really isn't that hard to do. Once you make this presumption, worrying about the local climate is irrelevant and nasty surprises are avoided.
John White, Shop Manager, Fine Woodworking Magazine
John, I'm well aware of that issue. I've lived and worked in both the UK and on the American Gulf Coast. Furniture I've made for both myself and clients has been shipped around the world from both the UK and the US. I'm well aware of the vagaries of putting furniture in conditions it's not designed for.
Here's just a small sampleof text from my manuscript that covers it. It's one of a series of bullet points discussed in greater depth elsewhere in the text. Slainte.
"Allowing for a greater range of Relative Humidity conditions than the items’ intended final home— these are conditions that the item might find itself in later in its life after installation in the building it was designed for. For example a piece of free standing furniture designed for a specific location may be transported around the world in a container on a ships deck. Secondly, at some time in its life the item might be stored in a damp barn at a coastal location, or in a hot arid storage facility near Alice Springs in central <!----><!----><!---->Australia<!----><!---->."Richard Jones Furniture
Obviously you are way ahead of me, and have covered the point well.
John W.
John, looking back at my earlier reply to you I've come to the conclusion it looks a bit snappily worded. That was not my intention.It might have been better phrased something like this:
I think I've got that issue covered. I've lived and worked in both the UK and on the American Gulf Coast. Furniture I've made for both myself and clients has been shipped around the world from both the UK and the US. I've experienced some of the vagaries of putting furniture in conditions it's not designed for.
"Here's just a small sampleof text from my manuscript --- blah, blah."
Anyway, it wasn't my intention to sound a bit short if that's the way you saw it. I apologise if it came across that way. Slainte.Richard Jones Furniture
Your text didn't come across as short or "snappy" at all, I thought it was well written and covered the point I was making perfectly. Everything is fine, no offense was taken.
Good luck with your tome.
John W.
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