air circuloation via ducting in large unheated room

Not quite the same, but I have long noted that thermal gain in South facing rooms is begging to be shared with cold North facing rooms. When we refurbished our current property I included an extractor fan and ducting to move the warm air.

I think I probably got my calculations wrong, or the stated air flow through the fan turned out to be very optimistic but the difference in air temperature in the cool room was not noticeable. Ducting is about the same diameter as soild drains IIRC.

From that I very tentatively conclude that you would need some "kick ass" ducting and fans to move the volume of air required to make a difference. Probably on the same lines as the ducting that you can crawl through which is used in industrial buildings.

I will nor read the rest of the thread!

Cheers

Dave R

Hmm...interesting comment. Now you mention it, the ducting used for ducted-air central heating is quite large, even in domestic properties, and that's moving quite warm air, much warmer than is likely to exist up near the ceiling in our Archive room. It's probably not such a good idea!

Finding ways to air seal to room and adding a dehumidifier might provide a big saving.

Sure it is.

Either use a ceiling fan, as in "industrial ceiling fan".

Or a floor fan,

or similar as a random example, fan pointing up.

Cold air forced upwards should mix, as would warm air forced down through a duct, but with less trouble in installation.

Thomas Prufer

Agreed, although you would need a strong enough fan. Otherwise the draught will have dissipated a few feet in front of the fan and all you're doing is mixing the air at the ground level.

One way to test this is to tape some torn strips of toilet paper to a broom handle and hold it in the air. You should be able to see the paper flapping at a high 'altitude'.

Theo

Surely, a dehumidifer would create its own air circulation by sucking out the humidity at ground level which will warm it.

It's an old school with tall windows, solid walls and a high ceiling. Nightmare to keep warm even if it doesn't have an intrinsic damp problem at ground level.

Yep, most of that, except there's no sign of damp at ground level.

A dehumidifier is certainly a consideration, and has been before. I suggested it a couple of years ago, but TPTB here were/are put off by the potential running costs, even more so now. The fan isn't particularly powerful though, and damp air is lighter than dry air at the same temperature so will accumulate up near the ceiling.

I like the idea of a powerful fan to blow a gale upwards. I'll think about it.

Thanks to all.

Err, in the absence of effective heating then the colder, damper air will be at ground level, surely ?.

I did say 'at the same temperature'.

And: Blow reaches further than suck, Bernoulli and all...

Note that a cubic meter of air weighs about a kilo. So any mechanism to circulate the air will need to run for a good length of time until the entire mass of air gets up to speed, as it were.

Thomas Prufer

Because of the layout of the building (one big room?, with solid uninsulated walls and tall, narrow windows and a high pitched ceiling - ex victorian? school, also with zero insulation), wouldn't just a heat source in the centre (where the pot-boiler used to be) create its own circulation ?.

I'd expect the heat to rise, and form a layer under the ceiling: I have been wrong before. I'd try and see, with an incense stick, and see where the smoke rises and falls...

Thomas Prufer

A dehumidifer is the way forward. Only dessicant wheel types are suitable where the space is not consistently warm. Ebacs are overpriced. I'd be very wary of any cheap Chinese combustion heater. Having looked at a couple once I'd keep a safe distance from them. Think they were Deathomatic brand. A safe used sealed vented gas heater would make more sense. HRV can be useful in the shoulder times, ie when outdoor temp is sometimes warmer than indoor. And they provide less energy losing ventilation when needed. If used when not needed they of course lose heat, the recovery efficiency isn't great. An RH meter would be a good place to start, otherwise you're guessing, which is very energy inefficient. £2 something from China, accurate to a few %. There are cheap ways to heat somewhat, but I hesitate to recommend them.

By the sound of it there is enough paper on the shelves to build a bonfire, assuming that paper is dry enough to light :)

Isn't the real answer with archives to digitise it all and then store multiple copies in various different places? Every 5 or 10 years transfer the digital information to the latest storage media available at the time.

If they can get the Bible's new testament on a pin head the whole archive shouldn't take that much storage space :)

My thinking also. A while ago we were given a small domestic dehumidifier, but TPTB have balked at running it in the past, I think because it was claimed they were 'expensive to run' (and that was three years ago!) without actually trying it out. I am about to run ours continuously for several weeks to see how effective it is and at what cost, continuously monitoring the temperature and humidity in the room with a data-logger and the electricity use with a power meter. We can then make some decisions based on facts rather than hearsay.

The dehumidifier claims to be effective down to 5°C. I hope it never gets anywhere near that low in the room. It's a Duracraft DD-TEC10E if that means anything to anyone.

I've been put off desiccant wheel types because of a comment here in the past that they have been known to catch fire, if the wheel jams and the little heater ignites the cardboard substrate carrying the desiccant. Not really the sort of heating we want to encourage in an Archive!

We are slowly working our way towards digitising it all, but it's a slow process, needs a lot of preliminary work, and volunteer numbers are limited.

We've been using a slightly bigger dehumidifier (a Dimplex - 400W) in our house for many years. It works well, but I assume you've got a schedule for someone to empty out the tank or it will just stop when full. Or will you mount it higher and use the water outlet to go to a much larger tank? Have you decided what RH level you will set it at?

Remember that the dehumidifier is effectively a small fan heater, so will add a bit of heat to the room. The "warmer" air will hold slightly more water, which will condense on anything cooler. That's of no help!