Condensation / warmth

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534 posts

Ultimate Geek

#794979 8-Apr-2013 13:34

It's worth understanding what causes window condensation. The temperature of the inside surface of the window goes below the dew-point of the air inside the house. Condensation starts to form which removes moisture from the air near the window. This is soon equalized with the air in the rest of the room and the process continues like a moisture conveyor belt untill an equilibrium can occur. With a double-glazed window, even though there may be some moisture inside the unit, condensation does not occur because the sealing of unit limits the available moisture.

Condensation doesn't occur on the outside of the window because the surface, warmed by heat from inside, is above the dew point of the outside air. On some houses, my own included, on a cold morning, you can see a pattern of moisture on the walls (insulated and cold) but also the outline of the frame without moisture(warmer due to thermal bridging).

Obviously, as mentioned, in a rental house your options are limited. Encourage your landlord to insulate by all means, perhaps there are still subsidies for him. The cheap film-glaze that you can get at hardware stores or Trade Me would be a good option as it should provide a good seal. Suggest you do a test to ensure the tape won't damage the widows on removal. Of course, try to keep the house as well aired as possible.

timmmay

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#794983 8-Apr-2013 13:37

lokhor: Wondering how much something like these would be to get installed:
http://www.superlux.co.nz/products/?id=343&product=1272

If you're going to replace your fittings replace them with something IC rated so you can cover them. They look to be CA rated, insulation up to but not over. LED fittings are $55 - $85 each, probably on the lower end now. You can buy them from lighting direct.

Since there's no re-wiring required just take a guess at how long it'll take an electrician. Four lights, maybe 30-90 minutes, say $70/hr. More lights will be much quicker since they're already up there with all their tools.

Stan

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#794997 8-Apr-2013 13:43

May have jumped in this a tad late but I work in the industry of home heating and ventilation.

The Aircon in your lounge will not be dragging moisture out of the Air on heating mode. Positive pressure ventilation is effective in older houses for reducing condensation but it will reduce the overall average temperature of your house.

However since your house is rented the best thing you can do is put a small dehumidifier down that end of the house or talk to your landlord about a more suitable solution.

Heat transfer is not something generally recommended with a heat pump as the heat pump is not designed to put out excess heat they do work better with a gas fire but they are really designed for a wood burning fireplace as they are often far more powerful than both.
EECA is about to release a study on heat transfer systems where they used a variety of fans of modes of heating I know there were some interesting results from this.

Modern gas fires do not affect condensation in there environment all that much particularly modern power flued models (ie Rinnai Arriva)

Any questions feel free to ask.

leo0787sx

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Ultimate Geek

#795025 8-Apr-2013 14:30

Thank you for all the help so far :)

We are unable to really move as we have pets and most 'new' places will not allow pets.

I believe we have some foil under the bathroom but not sure if it is the whole house. We have a heat pump in the living/kitchen area and I bought one of those eco heaters for the bedroom (the thin ones you can paint).

My Landlord has mentioned putting roof insultation in, which I have followed up on but the condensation seems to be the main issue as I'm worried about mould/damp conditions.

It seems a dehumidifier might be the best option in the corridor with all the rooms open.

Jaxson

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#795027 8-Apr-2013 14:31

Stan:
The Aircon in your lounge will not be dragging moisture out of the Air on heating mode.

Yeah Aircon and dehumidifier units dehumidify by passing the air over cold parts, which is essentially the same as what's happening when you get condensation on cold window glass. So, you get the benefits of this when you run your heat pump in cooling mode, but naturally no one is doing this in winter. Units with a setting for this, actually run cold air for a while and then return to the heating you need in winter. Either way it's going to cost you money.

In practise, heat transfer unit are only really suitable for use with wood burner fires, where you've got too much heat in one area. You lose heat as the air travels through the ducts which are up above the insulation. It's ok to shave 5 degrees off if you've started at say 35 degrees etc, but it doesn't work very well if you've only started at 21 degrees. Also you need to keep the doors open at least a bit, so the air can make it's way back to the lounge where it started the journey. Heat pumps in halls ways are not much use if all the bedroom doors are shut.

Positive pressure systems are a good idea, but need to be actively managed. You're taking outside air and pumping it directly into your house, in essence a draft you are paying for. When it's 4 degrees outside, this will rapidly cool the house, so they often have reheats in the line, which will again cost a fair bit to run. A timer etc would be sensible on this type of system, so you can actively control when the unit runs.

As others have mentioned before, on many other threads, there are pros and cons to everything, so be very careful of advertising material! Your options are also limited if you are renting. DIY secondary glazing is my favourite tip for renters. It ain't pretty, but it's cheap and I know for a fact that it works.

timmmay

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#795041 8-Apr-2013 14:37

leo0787sx: Thank you for all the help so far :)

We are unable to really move as we have pets and most 'new' places will not allow pets.

I believe we have some foil under the bathroom but not sure if it is the whole house. We have a heat pump in the living/kitchen area and I bought one of those eco heaters for the bedroom (the thin ones you can paint).

My Landlord has mentioned putting roof insultation in, which I have followed up on but the condensation seems to be the main issue as I'm worried about mould/damp conditions.

It seems a dehumidifier might be the best option in the corridor with all the rooms open.

Ceiling insulation will make the place a lot more comfortable, but probably won't help condensation. As it's warmer it may make it worse.

A dehumidifier will help. Good curtains will help. Making sure windows are opened during the day will help a lot too.

leo0787sx

407 posts

Ultimate Geek

#795050 8-Apr-2013 14:51

timmmay:
leo0787sx: Thank you for all the help so far :)

We are unable to really move as we have pets and most 'new' places will not allow pets.

I believe we have some foil under the bathroom but not sure if it is the whole house. We have a heat pump in the living/kitchen area and I bought one of those eco heaters for the bedroom (the thin ones you can paint).

My Landlord has mentioned putting roof insultation in, which I have followed up on but the condensation seems to be the main issue as I'm worried about mould/damp conditions.

It seems a dehumidifier might be the best option in the corridor with all the rooms open.

Ceiling insulation will make the place a lot more comfortable, but probably won't help condensation. As it's warmer it may make it worse.

A dehumidifier will help. Good curtains will help. Making sure windows are opened during the day will help a lot too.

We have really thick curtains and some are to the floor so guess we must have a pretty bad place. I would open windows but my partner has a fear of spiders, it took a while for her to let me leak the windows. Also I'm worried about getting the house broken into as we work away most days.

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timmmay

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#795053 8-Apr-2013 14:53

Closing windows when you're out is sensible. I have security locks, but you can't really fit them on a rental place.

lokhor

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#795066 8-Apr-2013 15:29

timmmay:
lokhor: Wondering how much something like these would be to get installed:
http://www.superlux.co.nz/products/?id=343&product=1272

If you're going to replace your fittings replace them with something IC rated so you can cover them. They look to be CA rated, insulation up to but not over. LED fittings are $55 - $85 each, probably on the lower end now. You can buy them from lighting direct.

Since there's no re-wiring required just take a guess at how long it'll take an electrician. Four lights, maybe 30-90 minutes, say $70/hr. More lights will be much quicker since they're already up there with all their tools.

ok I'll look into this. may be getting an electrician friend to come over and take a look at things, including installing an extraction fan in the bathroom so will see what he says about doing this.

All comments are my own opinion, and not that of my employer unless explicitly stated.

Stan

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#795204 8-Apr-2013 19:54

lokhor:
timmmay:
lokhor: Wondering how much something like these would be to get installed:
http://www.superlux.co.nz/products/?id=343&product=1272

If you're going to replace your fittings replace them with something IC rated so you can cover them. They look to be CA rated, insulation up to but not over. LED fittings are $55 - $85 each, probably on the lower end now. You can buy them from lighting direct.

Since there's no re-wiring required just take a guess at how long it'll take an electrician. Four lights, maybe 30-90 minutes, say $70/hr. More lights will be much quicker since they're already up there with all their tools.

ok I'll look into this. may be getting an electrician friend to come over and take a look at things, including installing an extraction fan in the bathroom so will see what he says about doing this.

When it comes to bathroom extraction you want around 10 changes of air per hour.
Easy way to calculate that is m3 per hour (ie 2mx3mx2.4m=14.4m3x10=144m3 per hour) that is the minimum size fan you should go for these cheap heat light fan units that are floating around generally will struggle to do 100m3 per hour.

timmmay

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#795206 8-Apr-2013 19:58

Those light fan units are hopeless. The one my Dad has barely moves any air.

The first one we got in our new bathroom was a massive thing, like a car tyre. It sucks so much air through that even in summer it made the bathroom feel cold. They replaced it with one more like a motorcycle tyre, two speed, so now we can choose. On low it probably still does 5-10 times what those light/fan units do.

Stan

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#795213 8-Apr-2013 20:23

timmmay: Those light fan units are hopeless. The one my Dad has barely moves any air.

The first one we got in our new bathroom was a massive thing, like a car tyre. It sucks so much air through that even in summer it made the bathroom feel cold. They replaced it with one more like a motorcycle tyre, two speed, so now we can choose. On low it probably still does 5-10 times what those light/fan units do.

They are rather rubbish move roughly 30L/s (litres of air per second). Most of them are all mass imported crap from china by various brands.
Even the manrose "pro series" heat light fans are only suitable for a small bathroom moving 60L/s.

Dedicated 150mm inline fan from either manrose or wiess is what is needed for a standard bathroom. These tend move around 89L/s+.

Also make sure your have an air gap under your door, the fan will not perform if you turn your bathroom into a vacuum.

Alternatively you could throw an EBM 200mm centrifugal fan and move the entire air volume of your bathroom every minute :P

Niel

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#795221 8-Apr-2013 20:27

We built a new house in Auckland 2 years ago after living in a 1960's uninsulated house for 9 years since we migrated to NZ. In Winter we still get some condensation on the window frames despite a thermal break (and double glazing), but as we are engineers we actually expected this as we understand it will still be colder than anything else in the house.

Last year we replaced all the incandescent bulbs in the down lights (which are not IC) with LED bulbs which actually fills up most of the opening to the ceiling and allows only a minute draft which vents the home and cools the LED bulb. It is really minimal, not nearly as bad as with an incandescent bulb, and the house gets stuffy if there is no wind (i.e. it is minimal leakage). Yes there is a hole in my insulation, but people with heat transfer and DVS and whatever else do not realise their insulated ducting is still R0.6 at best.

If I was in a colder area like Christchurch or Wellington then certainly would go IC rated fittings, but in Auckland I'm working with what the builders gave me until I find a suitable LEDs fitting that I like that will fit the odd size 120mm hole and after I have done all the other more important upgrades.

I am about to fit an air circulation kit (not ventilation) which will draw stale humid are from bedrooms and blow it into the living space so that airconditioned air from the living space can be drawn through the passage into the bedrooms. My ducting will be on top of the insulation, but I'll cover the ducting with a layer of pink batts.

You want to get humid air out of the South-side rooms, and if you do not want to loose the heat (passive heat exchangers recover less than 50%), then circulation is the only option.

We installed an aircon in December. It is turned on most of the weekend, and weekdays from mid afternoon 'till morning. Temperature during the day is set at 23 degrees and during the night 25 degrees, and we only use cooling mode. The aircon does not run much even during the recent hot weather, and our power bill is similar to 12 months ago - most of our power use is hot water, stove and tumble dryer. Even with the recent cold nights and 7 degrees outside in the morning, I still sleep in only shorts and under only a duvet (no blanket). When I get up in the morning I also do not get cold unless I have to fetch clothes in the uninsulated garage.

What I have learned from my old home is seal the gaps around windows, use heat lamps with ventilation in the bathrooms, and go double glazing (I did it on the cheap by sticking plastic sheets over the frames, made a big difference). This is assuming you have done insulation and a ground moisture barrier (which btw. we did not do in the old house).

This morning my project leader and I actually talked about ceiling insulation, he is clued up on the subject as he designed and built his own house over the past few years as an experiment in efficiency (his daughter studied architecture during the same time). His comment is that batts by themselves is not enough. You still need to close in the envelope to trap air around the batts. There are a few products on the market which you drape across the ceiling and nail to rafters. Or what he did was to use batts and polystyrene together. For example ceiling batts by themselves with R5 rating does not give you an R5 insulated ceiling, because the timber rafters are not R5 (they are R4 at best, which is why someone posted he can see the framing outline on his outside walls). So the person that posted he put old batts over the rafters and has R5 batts, you did the right thing - a sheet material would be better though, but cost money and the old batts is still a good result.

Don't know where the OP lives, but I do have a window mounted aircon available if you (or someone else) are interested. I'm in East Auckland. I had it mounted in our old house by unscrewing a window (hinges), attaching a bracket + shelf to the window frame, placing the unit on the shelf, and closing in the gap around the unit with timber and silicone. When we sold the house I removed the aircon unit and bracket, and screwed the window back in. It was 3kW output (1kW consumption) heating ~70 sqm house to 18 degrees C year round except a few weeks around October when the outside of the unit would freeze up during the early morning hours.

While you cook, use the extractor fan to remove steam. And clean the filter. When you are done cooking, open the oven door to get a burst of hot air out of the oven instead of a slow cooldown - it is not more efficient but will help psychologically when you feel the heat.

For the bedrooms use a few small electric oil fin heaters at a lowish to mid setting and switch to half power, then put an old CPU fan on top running off an old power adapter of about 9V (12V is too fast) blowing down on the heater so that the heat is spread across the floor instead of just rising to the ceiling. This is how we heated our new 200 sqm home for one Winter using 2x 6-fin heaters until we got a heat pump installed this Summer. During that Winter only half our down lights had LED lamps, so the other half were still draughty.

BTW our doors and windows are always closed as it keeps dust out (busy landscaping, have not had lawn for over 2 years now), keeps flies + mosquitoes out, and keeps the heat/cold in. We need a little bit of leakage through light fittings to keep us alive ;-).

You can never have enough Volvos!

Niel

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#795226 8-Apr-2013 20:32

Stan: Alternatively you could throw an EBM 200mm centrifugal fan and move the entire air volume of your bathroom every minute :P

Centrifugal fans are great indeed, they can push/pull air. Axial fans are (apparently) quieter, but their air flow rating is with no ducting attached and they cannot handle long runs (more than a few meter). 3-in-1 fittings use centrifugal fans, but they usually have poor "blades".

You can never have enough Volvos!

richms

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#795231 8-Apr-2013 20:41

lokhor: Wondering how much something like these would be to get installed:
http://www.superlux.co.nz/products/?id=343&product=1272

CFL - dont bother when there are cheap LED lamps available everywhere now. Only issue with the oribt ones at mitre10 is you have to like crusty orange light as that is all they make them in, but they are so cheap now that looking at anything with a CFL in it is IMO foolish.

Richard rich.ms

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