Condensation / warmth

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#795246 8-Apr-2013 21:08

Anyone know what type of fan this is? It's maybe 30-35cm diameter, and it pushes a lot of air through. I could go look, but it's in the ceiling and I'm too lazy to pull the stairs down, plus it does a great job anyway.

The original fan was quite a bit bigger again.

Niel

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#795260 8-Apr-2013 21:35

I would guess centrifugal due to the cone shape at the exhaust, and because an axial fan blades are the same size as the inlet/outlet/housing.

You can never have enough Volvos!

Stan

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#795295 8-Apr-2013 22:28

Yeah looks like a centrifugal fan unsure of brand I will have a bit of a look through some of the older info I have at work.

You should tighten up that duct if you feel like getting a bit of extra free performance.

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#795298 8-Apr-2013 22:39

leo0787sx: Hello,

As the cold is coming I was wondering if you had any ideas / advice or something I can do to reduce condensation / warm up the house?

A few additional points that I haven't seen anyone mention:

Don't dry or air washing inside. Even damp clothes give off a lot of moisture. It has been no more expensive to to use our electric clothes dryer than to air clothes inside and the atmosphere is noticeably drier.
Make sure your clothes dryer vents outside. If it doesn't then it will be like pouring water into your house so use it in a room that is very well ventilated and that can be shut off from the rest of the house.
Don't leave wet towels and flannels around. They take up a lot of water when we use them which will gradually evaporate in your house. We have several people in our house having showers every day so leaving the fan on in the bathroom helped a lot with the damp clothes basket. We now make everyone put their towels in the laundry which is largely separate to the rest of the house.
Have curtains that insulate and prevent airflow when they are closed. My wife just makes a liner or puts the new curtains over the old ones provided there is no colour or pattern showing through the new ones. We curve the curtain rails around towards the walls at the end to get a good seal. And where it looks OK the curtains go all the way to the floor. This reduces condensation as moisture and air flow are limited.

Further to what others have said:

Insulation has a very positive payback. For example, putting a $200 cylinder wrap on an older hot water cylinder can payback in six months as you only have to save about 800 units of power (kWh). One US study I read said that they got a positive NPV from up to about 17 inches of insulation on a hot water cylinder which has water at about 70C.
Even if you have batts in the ceiling it is still worth getting blanket insulation over the top. The blanket reduces air movement and convective losses. It's better than nailing/stapling a sheet over the old batts. We used a polyester blanket which, with our steel roof, has made the house much warmer in winter, much cooler in summer and quieter in the rain.
Re covering downlights, I have heard of metal mesh waste-paper baskets being used (like the plastic buckets mentioned).

leo0787sx

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#795395 9-Apr-2013 09:43

We are in Christchurch so one of the colder areas, it wasn't too bad this morning but I still had to wipe the windows. I guess I'm clueless due to the face I'm from the UK, I miss radiators :(

Most rooms have blinds and curtains, some only blinds, wheere we can we have both closed to try and keep warmth / stop condensation.

Kitchen has an extractor fan on the hub

The bathroom has one of those light fans but it seems to do a good enough job as there's only two of us.

The main room (living and kitchen) has an aircon

Main Bedroom has a small eco heater

No wall or ceiling insulation and probably no special light fittings.

Clothes are outside unless it rains otherwise in the main room with a window open - have thought about getting a dryer

All rooms have a gap under the door and windows leaked. Should we cover the bottom of the doors and close and seal the windows instead?

Landlord has said they are happy to buy a dehumidifier around a few $100 so looked at: http://www.noelleeming.co.nz/shop/heating-cooling/dehumidifiers/sheffield-pl420-dehumidifier/prod46101.html which we would put in the corridor to work on the 3 bedrooms and bathroom probably an hour before bed and an hour when we get up? Would this work?

Thank you for all the help guys, really appreciate it.

jpoc

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#795407 9-Apr-2013 09:49

Three tips to fight condensation.

Condensation tip 1 - Get (or make) a shower dome and use it correctly.

If your shower is suitable for a shower dome and you do not have one then buy one or make one yourself.

They work.

You can make one easily enough with some corrugated cardboard, plastic sheet and duct tape.

Cut the cardboard to suit, you can opt for a flat top or, with a bit more effort you could make something that looks like a traditional house roof. That will give you a little more headroom inside. Use the plastic sheet to cover the cardboard and thus keep it dry.

A shower dome will work well and will reduce condensation by a large amount but if you take a little extra care, you can gain even more benefit! At the end of your shower, do not just turn off the tap and get out. Turn the water temperature down to as cold as you can and spray cold water on the walls of the shower and also around you in the air inside the shower cubicle.

What good does that do?

Consider the state of the bathroom and shower at the end of your shower. In the bathroom, you have a large volume of air at, say 22 degrees and 80% humidity. In the shower cubicle, you have a smaller volume of air at perhaps 35 degrees and 100% humidity. When you open the shower door, the air will mix up and you will increase the humidity of the air in the bathroom and you may see some amount of condensation. It depends on the room, the temperatures and the humidity and there will never be as much as without a shower dome. If you chill the shower just before you leave it, the air in the shower will be at say 18 degrees still with 100% humidity. The important thing to remember though is that air at 18 degrees and 100% humidity contains a lot less water than air at 35 degrees and 100% humidity. When you exit the shower and the air mixes, the air that was in the shower will be warmed thus reducing its humidity and so you will not see any condensation in the bathroom.

Condensation tip 2 - Change you cooking style.

Boiling food in water will always put water into the air and that water will come out elsewhere as condensation. Even if you have an extractor fan in the kitchen, it will not be 100% effective so there will always be some extra water in the air and that will lead to condensation.

Many vegetables can be cooked in a plastic box with a spoonful of water in the microwave. Frozen peas are easy, you are not really trying to cook them anyway, just warm them up and they do fine in a microwave. It takes a little longer with stuff like broccolli and sliced carrots as you are cooking them to make them soft but it still works just fine and you can use the same technique for hard pasta. I have a bench-top mini-oven/grill and I use that for a lot of stuff. I cook sweetcorn in mine - just put the whole thing in including the green husks and cook until the green parts begin to turn dark brown. Peel back the husks and you have perfectly cooked corn. No need to boil.

Condensation tip 3- Opening windows does not get rid of condensation. Closing them does - so do it as often as you can.

Consider the physics of opening and closing your windows on a cold damp winter's day. Let's say that you start out with a room at 25 degrees and 80% humidity and the outside conditions are 5 degrees and 80% humidity. The inner surface of your windows will be at just a little more than 5 degrees and so the air next to the glass will be chilled and water will condense on the glass. So, you open some windows because we all "know" that you do this to get ventilation to fight the condensation. So what happens to all the condensation on your windows? Nothing. It does not go away at all. Why? When you open the windows, the air will mix and, because there is so much more air outside than inside, the air in the room will approach the same conditions as the air outside - that was 5 degrees and 80% humidity. Air at 80% humidity is not going to pick up a lot of water so your condensation will stay on the windows.

Now consider what happens if you close the windows just a couple of minutes after you open them. When you close the windows, the air in the room has already mixed with the air ourside so it is not far away from being at 5 degrees and 80% humidity. You did not leave the windows open for long enough to chill the room itself so the walls, floor and furniture are still at 25 degrees and in the next couple of minutes, the air will warm up to the same temperature. That will drop the humidity substantially. No more condensation can occur. The inner surface of the glass by the windows will still be cold and will still chill the air there down to little more than the external temperature but that is OK. The air in the room now contains less water than before and even near to the glass, it cannot exceed 80% humidity so it will no longer condense. In fact things are better than that. The overall humidity in the room will have dropped as the air warmed back up and it will start to suck back the condensation. After about thirty minutes, that process will have stopped, the air will have picked up as much water as it is going to and it is time to open the windows again for a couple of minutes and then close them and allow the process to repeat.

freitasm

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#795411 9-Apr-2013 09:57

Sorry, but I can't understand the relationship between the thermodynamics and the water in the air in your explanation.

The inside air still at 80% but the condensation goes away. Sure, but it's still 80% so it's still damp. I understand if one were to put a dehumidifier in for example and collect that dampness then we slowly could get less condensation. But opening the window again would make the whole thing damp again, and continue the process?

What am I missing here?

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timmmay

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#795421 9-Apr-2013 10:11

Stan: Yeah looks like a centrifugal fan unsure of brand I will have a bit of a look through some of the older info I have at work.

You should tighten up that duct if you feel like getting a bit of extra free performance.

Tighten it up where/how?

Don't worry about identifying it, I could look at the label if it was important. It works great.

freitasm: Sorry, but I can't understand the relationship between the thermodynamics and the water in the air in your explanation.

The inside air still at 80% but the condensation goes away. Sure, but it's still 80% so it's still damp. I understand if one were to put a dehumidifier in for example and collect that dampness then we slowly could get less condensation. But opening the window again would make the whole thing damp again, and continue the process?

What am I missing here?

Agreed. Also air at low temperatures can't hold as much water, so it's less humid. I think that whole topic is a red herring, but I'm willing to be convinced otherwise.

jpoc

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#795446 9-Apr-2013 10:43

freitasm: Sorry, but I can't understand the relationship between the thermodynamics and the water in the air in your explanation.

The inside air still at 80% but the condensation goes away. Sure, but it's still 80% so it's still damp. I understand if one were to put a dehumidifier in for example and collect that dampness then we slowly could get less condensation. But opening the window again would make the whole thing damp again, and continue the process?

What am I missing here?

Suppose that the size of the room is such that at 25 degrees C and 80% humidity, the air contains 16 grams of water vapour. If there is a breeze blowing, we can open two windows and air from outside will blow in through one window and air from inside will be blown out through the other window. So now the room is full of air at 5 degrees and 80% humidity. But that air will only have 5 grams of water vapour in it. We blew out air that contained 16 grams of water and brought in air that contained 5 grams. We close the windows and the air warms back up to 25 degrees. It still only has 5 grams of water. So overall in the room, the humidity has dropped to 25%. By the window, where the cold glass is only a little warmer than outside, the humidity cannot get above 80% so there will be no more condensation. In fact as the air circulates in the room, we have air at 25 degrees and 25% humidity encountering the cold glass. That air will cool down but as it does so, it will still be at low enough humidity to pick up the condensation that was previously deposited. After thirty minutes, the air in the room will have picked up another 11 grams of water from the condensation to get back to the point at which it will pick up no more water. Then we open the windows again and the air that passes out will carry 16 grams of water while the air that comes in will again contain just five grams. We repeat the process until all of the condensation has gone.

Of course, we will not get perfect replacement of air when we open the windows and there will be additional sources of water entering the air in the house (cooking, breathing, showering etc) but the effect still counts and every time we cycle the air in and out we eject a few grams of water vapour from the house.

Handle9

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#795466 9-Apr-2013 11:03

timmmay:
Stan: Yeah looks like a centrifugal fan unsure of brand I will have a bit of a look through some of the older info I have at work.

You should tighten up that duct if you feel like getting a bit of extra free performance.

Tighten it up where/how?

You've got kinks in your duct - every bend costs performance as it introduces resistance. You want long and smooth runs to maximise performance.

Jaxson

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#795467 9-Apr-2013 11:07

timmmay:
Stan: Yeah looks like a centrifugal fan unsure of brand I will have a bit of a look through some of the older info I have at work.

You should tighten up that duct if you feel like getting a bit of extra free performance.

Tighten it up where/how?

Take the duct as it stands (on the left of your picture for instance, where it's currently all draped and bendy), pull it out tighter and cut the excess off. This leads to a smoother inside wall edge, which offers less resistance to air flow than you would currently be achieving.

Jaxson

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#795468 9-Apr-2013 11:12

jpoc:

Condensation tip 3- Opening windows does not get rid of condensation. Closing them does - so do it as often as you can.

I know where you're coming from, but the way you've worded this line is very likely to confuse.

Perhaps rephrase as:

Condensation tip 3- Don't leave your windows open permanently. Open your windows often, but for short periods of time only (up to 5 minutes open time), to flush out the stale moist air in the room. Then close the windows again so you don't lose too much heat.

timmmay

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#795469 9-Apr-2013 11:14

Thanks for the info about the bent ducts, I understand now. It was installed by an electrician and works fine, if anything I want less airflow not more! That thing really sucks. I have to turn it off after a shower when I'm standing in the bathroom as I get too cold with the air flowing past!

jpoc:
Suppose that the size of the room is such that at 25 degrees C and 80% humidity, the air contains 16 grams of water vapour. If there is a breeze blowing, we can open two windows and air from outside will blow in through one window and air from inside will be blown out through the other window. So now the room is full of air at 5 degrees and 80% humidity. But that air will only have 5 grams of water vapour in it. We blew out air that contained 16 grams of water and brought in air that contained 5 grams. We close the windows and the air warms back up to 25 degrees. It still only has 5 grams of water. So overall in the room, the humidity has dropped to 25%. By the window, where the cold glass is only a little warmer than outside, the humidity cannot get above 80% so there will be no more condensation. In fact as the air circulates in the room, we have air at 25 degrees and 25% humidity encountering the cold glass. That air will cool down but as it does so, it will still be at low enough humidity to pick up the condensation that was previously deposited. After thirty minutes, the air in the room will have picked up another 11 grams of water from the condensation to get back to the point at which it will pick up no more water. Then we open the windows again and the air that passes out will carry 16 grams of water while the air that comes in will again contain just five grams. We repeat the process until all of the condensation has gone.

Of course, we will not get perfect replacement of air when we open the windows and there will be additional sources of water entering the air in the house (cooking, breathing, showering etc) but the effect still counts and every time we cycle the air in and out we eject a few grams of water vapour from the house.

Ah I get you now. You're basically saying that ventilation is good to reduce humidity, and confusing us with numbers. Yes reducing the moisture in the air is good, but losing heat is bad. I'm not sure cycling windows is a practical solution.

Jaxson

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#795479 9-Apr-2013 11:35

Technically you can get pooling of water in those extraction fan ducts also, where the warm water laden water is cooled as it travels through the non insulated duct, eventually condensing back into liquid water. It's a good idea to have the last leg of the duct angling down to it's eventual outside outlet, so any liquid will run downhill and drip outside.

timmmay

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#795482 9-Apr-2013 11:41

Good point, I bet that's especially true in winter. I'll sort it out on the weekend, thanks :)

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