House humidity

[RichD1]

I've was given one of those weather station clocks a couple of years ago which measures humidity. I didn't believe that we had a humidity problem but the measure has always been in the 60% to 70% range apart from really dry spells in the summer when it would drop to 55% to 60%.

We always open windows whenever possible, have a cooker extractor to outside and extractors in the bathrooms and open the windows once finished. We don't suffer from mold growth anywhere, we do get a small bit of condensation on the bottoms of the DG when really cold and in the front bedrooms as the large bay windows face north. I've now installed secondary DG and this has helped tremendously.

My question is how do you get the humidity lower without the use of a dehumidifier?

Have recently built a new timber framed and fully insulated workshop and the measurements in there are around 72%.

Any advice will be greatly received.

Richard

 

[Jacob]

What is the problem, or why do you think you have a problem?

 

[KevM]

I suspect the sensors in most domestic units are pretty rudimentary, here's an article that discusses a similar issue:

http://www.telegraph.co.uk/property/pro ... -home.html

It might be interesting to attempt a calibration, although I'm not quite sure how you could achieve the calibration set points in a domestic environment. However, maybe find a Tupperware (other brands are available!) box just large enough to take the sensor and a couple of fresh silica gel desiccant packs (or uncooked rice), leave the box sealed up for a few hours (or until there is no further change) in a warm place, this should take you down to single digit humidity, repeat with some well dampened kitchen towel in place of the desiccant, this should take you to the 90's. It's not really a calibration, so much as a means of determining the range of the sensor.

Where the sensor is situated is probably more important than the measurement accuracy of a sensor that should be considered 'indication only' at best. Unless you're experiencing problems from the damp, mildew, etc, you're probably just in the range of humidity for UK properties.

 

[Spindle]

Hi

Please don't take this the wrong way, but are you confusing relative humidity, (RH), with water content? See link for info on RH, in particular what is 'normal'

http://en.wikipedia.org/wiki/Relative_humidity

Also have a look at a weather site - the RH in Aberdeen today is 64% - the Isle of Portland 63%

Regards Mick

 

[MickCheese]

Using a humidity gauge in my workshop it usually reads about 60% and I didn't think that was too bad.

Is it?

Mick

 

[Spindle]

Hi

My workshop is integral to the house and ranges between 60% - 70%, never noticed any form of problem

Regards Mick

 

[KevM]

I've got a cheap thermometer/hygrometer sat in the living room and it's saying 47% inside and 57% outside at the moment, I wouldn't be surprised to see some slightly higher than usual readings at the moment, particularly in outbuildings, we've been having a spot of weather.

Apparently the cigar aficionados are well into their hygrometers and many use the salt test to calibrate (well at least achieve a single point calibration) at 75% RH, which as luck would have it is close to your measurement range.

http://www.cigarsinternational.com/ciga ... /salt-test

With Winter here, the cool, crisp conditions have likely altered the environment inside your humidor. So, you'll want to keep a close eye on your humidor. But how do you know that your hygrometer is reading the humidity accurately? A simple calibration will do the trick. Here are a couple of ways to calibrate your hygrometer:
The Towel Test:
Dampen a towel (not dripping wet, but good and damp), then wrap the hygrometer in the towel for 30 to 45 minutes. Then unwrap it and read the humidity (quickly). If your hygrometer is perfectly calibrated (few are) it will be reading exactly 100% humidity. Most likely, it will be reading somewhere between 80 and 90%. At this point, whatever the hygrometer reads, you can either set the needle to exactly 75% immediately after the test, or if you're a little lazier, make a mental note of how far over or under the actual humidity is from the reading from your hygrometer.
Wanna get a little more technical? Try the Salt Test:
Luckily, as nature would have it, when salt and water (NaCl and H2O for you studious types), are in a saturated solution at equilibrium, the resultant humidity is 75%. This gives a fantastic reference point to calibrate our hygrometer. There is an easy way to determine if your hygrometer is accurate. Here's the procedure you should use: you need a ziploc bag, a screw-on beer bottle cap (or other small container) a small amount of salt (regular 'ole table salt), and water.
Place the salt in the bottle cap (or other small container).
Dampen the salt with water. Do not put so much in that the salt gets "sloppy". You want a damp pile of salt in the bottle cap.
Place both the hygrometer and the bottle cap full of damp salt in the ziploc bag and seal it well. (It is important not to let air on or out while the test is going on.)
Keep it like this for over 8 hours.
After 8 hours in the damp salt environment, the actual humidity inside the bag will be 75%. Compare it to your hygrometer, your hygrometer should also read 75%. If not, you will then know exactly how far off your hygrometer is. If it's off, note the amount and direction that it actually reads and be sure to add or subtract that amount when reading the hygrometer. If the hygrometer has a control to adjust it (either the needle or the display), you can set the hygrometer to 75% immediately after the test.

You should salt test your hygrometer every 6 months or so to be sure of the accuracy.

 

[KevM]

Okay Science lab time - measure your own dewpoint! All you need is a glass of water, some ice cubes, a reliable thermometer - then use this rather spiffy online calculator: http://andrew.rsmas.miami.edu/bmcnoldy/Humidity.html

Of course, you'll have already calibrated your thermometer :wink:

This post on a musical instrument maker's forum explains it all: http://www.mimf.com/phpbb/viewtopic.php ... 01&p=15568

 

[MIGNAL]

The readings that you are obtaining aren't that far from 'normal', i.e. they don't seem that unusual to me. Quite often in very cold/snowy weather the humidity can drop down to below 30% - which is partly why we sometimes experience cracked lips in such conditions.
Some Hygrometers are very inaccurate, so you will need a method of testing it. The easiest is the salt test. NB. That the hygrometer will only be reliable at the % that you test it at. Different types of salt will allow you to test over a greater range.
It's very difficult to reduce the humidity in a room by any large percentage. The air exchange usually limits things to single figure reductions. An industrial scale dehumidifier really needs to be employed for very significant reductions.
Very small, tightly sealed rooms are relatively easy, even for a domestic sized dehumidifier. A heater contained within a small enclosure will also reduce RH within that enclosure.

 

[MMUK]

The best way of calibrating a hygrometer IME, is by using the Vaisala HMK15 humidity calibrator.

http://www.vaisala.com/en/products/humi ... HMK15.aspx

OK it's a bit OTT for domestic use but I have one for use on certain customer sites anyway.

 

[Jacob]

If condensation is the issue don't look at a hygrometer at all - look at walls, windows, etc. to see if you have a condensation problem.
RH can vary from near 0% (very cold day outside with heating on inside) to 100% (e.g. steamy shower room) in the ordinary course of events.
If you have condensation showing anywhere then the RH has reached 100% in that location at some point e.g. just in front of a steamy window.

 

[wellywood]

If it's not a problem - don't fix it. We ran a dehumidifier a number of years ago and it dried the building fabric so much (it's a timber frame house) that the walls in the bathroom shrank apart and the shower rail fell down. Think of any nice pieces of furniture you have that are acclimatized to your conditions and what a dry environment might do to them.

 

[RichD1]

Hi Guys,

Lots of interesting points made, I'll give them some consideration and report back. We don't have a huge condensation problem as such but reading the articles on the web suggests a good RH at around 50%, with ours being in the mid 60's I thought it might be an issue.

One measurement I have done is checking our bedroom RH just before going to bed which was 61%, this increased to 64% overnight. When we opened all the windows on the morning, within 10 minutes it had dropped to 56%. Closed the windows and it started going back up straight away.

Going to carry out some more experiments.

Richard

 

[Graham Orm]

Our house is a mansion, (modern terraced) front room has door to porch then street, door straight through to kitchen with door to rear garden via conservatory. This gives as much air flow as you could hope for with doors at both ends opening regularly. Our humidity is currently at 69% with heating on regularly at both ends of the day. I would guess this is as 'normal' as you will get in sunny Manchester.