Ducted air con system versus Crying windows

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knoxy2006, Jun 29, 5:08pm
We a looking at getting a ducted air con system for our 1970 brick house with full height single glazing (everywhere). My question is crying windows, our house has exterior windows to 25% of the exterior walls and on cold nights at 4 degrees or below we wake up to crying windows.

We have good full height curtains, along with extraction fans to the bathrooms and kitchen.

Will a ducted system with air movement throughout the night get rid of crying windows.

We are based in Palmerston North.

tweake, Jun 29, 5:29pm
i'll go out on a limb and say yes.
one of the tricks ventilation companies do is set the vents up so it blows across the ceiling and down behind the curtains. this stops condensation forming but at the expense of the curtains insulation value.
kinda of a catch22, the better curtains you have the more heat you retain but the worse condensation you get.

a simple way to trial it is to leave a curtain open on one side of the window. see if it gets condensation.

you can add ventilation to a ducted heat pump system.
but also make sure you have basic moisture sources fixed first eg underfloor moisture barrier.

knoxy2006, Jun 29, 6:02pm
Thanks tweake, I have a concrete floor so alright on that front, I have a moisture meter in the lounge and as the heat pump goes the moisture content reduces so that may help (no ducted system yet) . I will try leaving some curtains open as I'm open to your theory. I guess the other theory is I leave the heat pump on all night on a low setting for airflow and moisture reduction. Ps we only have one heat pump at one end of a really long house so we have a warm lounge but 4 bedrooms and 1 office are unheated.

nadznz, Jun 29, 6:53pm
We put in a ducted heat pump a couple of years ago. I can’t really be sure about the condensation as we have double glazing so that probably helps but we don’t get any. I do have to say the ducted heat pump is probably the best choice we’ve ever made though. Great for heating but this house also gets a lot of sun so awesome for cooling in summer. (Also in Palmy).

tweake, Jun 29, 7:05pm
the relative humidity changes with temperature, so by heating air drops the humidity. but as it cools down the humidity goes back up.
just heating it doesn't always change condensation as its more of a function of how cold the window gets rather than how hot the room is.

you could try leaving heat pump on low heat but i would just try leaving it on fan mode.
however its air flow is a bit different than a ceiling duct outlet so not sure if it will have any effect. tho its simple and cheap to test.

tygertung, Jun 29, 7:06pm
The cold windows cause condensation if the air in your house is damp and the cold windows lower the adjacent air to the dew point of the air which causes condensation. The moisture is caused by things such as breathing, damp clothes, cooking, washing etc. I notice in my house with single glazed windows that bedrooms will have condensation on the windows if the door is closed overnight, but if the door is open to the rest of the house, no condensation.

tweake, Jun 29, 7:30pm
define damp.
what level of humidity (and temp) is damp?

knoxy2006, Jun 29, 7:36pm
Can I ask what sort of cost your ducted system cost and the size of your house. We have 215m2, and recommended 10-11KW system, verbal 15k, but a formal quote to follow. We will get a heap of sun in lounge, dining and kitchen so cooling will be very handy indeed. It would be nice to live in the house for a whole year before making a decision but I think I can't go wrong with the outlay of a ducted system. I'm happy
to hear that you're please with your decision to get one.

knoxy2006, Jun 29, 7:38pm
I'm picking maybe they're meaning drying washing inside perhaps., a big no no but it happens.

joanie32, Jun 29, 7:52pm
We have a 1960s brick home

Last Saturday we shampooed the carpets and had 90% humidity inside

48 hours later it was back to 50%

My secret was opening windows a bit longer and throwing a couple extra logs on the fire

And that’s without a fine day yet.

It doesn’t have to be complicated.

tweake, Jun 29, 8:09pm
i don't know what insulation you have but i think that heat pump wattage is really really low.
i have that in northland in a house half the size (and possibly better insulated).

pay to run it through one of the calcs. there is the govt one they use for healthy homes.

sooperdoopa, Jun 29, 8:14pm
Might be worth getting a few more quotes as 11kw sounds a bit light for 215m2. Getting the wrong size will really suck.

nadznz, Jun 29, 9:31pm
Ours was installed in June 2018 @ $11,479 (incl).
16.0kW heating
14.0kW cooling
House is 231sqm
Outlets in 4 x bedrooms, dining room, lounge, living room and kitchen.

Definitely get more than one quote. We found them vastly different in price and in where they wanted to put the air intake/return things.

tygertung, Jun 29, 9:35pm
No, just coming in from the outdoors if it has been raining. Not worth it to try to dry clothes inside as we only have a heat pump, just dry as much as possible outside during this time of year then bung into the dryer.

It isn't so bad if you have a log burner as you have unlimited heat then.

gilligee, Jun 29, 10:01pm
We used to have weeping windows throughout the house but not since we installed double glazing. Wonderful.

knoxy2006, Jun 29, 11:06pm
Thanks for the info, I'm looking at getting another couple of quotes, thought I'd get one in hand first and have a good read before getting another. I think I'm getting a quote for a fresh air and heat recovery system, maybe this one - Mits Lossnay Home Ventilation System.

amasser, Jun 30, 6:18am
If O/P intends to stay in that house, it could be done in stages and a better investment.

joanie32, Jun 30, 7:21am
The single best thing we have done to cool the house in summer was to change the colour of the roof

It was black and is now Titania (off white)

That and planting deciduous trees in the right spots.

stylus1, Jun 30, 8:24am
we installed honeycomb blinds and that stopped condensation https://theblindstore.co.nz/honeycomb-blinds/ you still get some weeping on the frame even with double glazing. Make sure you have a showerdome installed.

tygertung, Jun 30, 8:26am
You would want a system where you can choose which areas you are heating, as there is no point in heating areas of the house you are not using.

Our house is probably 200 m2 and we have a 8 kw heatpump downstairs and a 6 upstairs, it is fine. We heat the areas of the house we are using.

shanreagh, Jun 30, 9:22am
I think in order of priority I would start on fitting double glazing before embarking on a whole house heating system. * But see later for ideas to upgrade curtains

Do it in stages from the coldest side first if money is a factor. I would also look at installing a simple system such as HRV or similar.

Only after doing this and when all the double glazing is done would I look at whole house heating.

I am assuming all the underfloor, wall and ceiling installtion has been done/upgraded.

*Curtains are not all created equal. If you have unlined thermal drapes then these need to be removed or lined. They attract mould like crazy, .especially where you have weeping windows.
If you line them at least you can renovate the lining if mould does occur.
by slicing a piece of the bottom and replacing with another piece of lining.

They need to be lined and floor to ceiling. If you want you can add detachable linings. Pelmets are good. If no pelmets then lift the curtain railing up and install them on the wall above the windows so the curtain skims the wall before reaching the window frame. .

tweake, Jun 30, 11:01am
trouble is insulation does not create heat.
however installing heating first means it will be a tad oversized once the windows are done.
it all depends on if both can be done and what sort of time frame.
if i had to pick one i would pick heating, at least you will be warm.

tweake, Jun 30, 11:06am
i think the whole "heat the room you use" is somewhat old fashioned.
its far better to heat the whole house.
but you need to consider how the rooms are used. ie the bedrooms you probably want a bit cooler, they could be done as one zone. the office may want its own separate system depending on how thats used.

tygertung, Jun 30, 11:22am
It is only a logical method based on efficiency. I don't believe it is worthwhile heating unused areas. Seeing as a house is not a vacuum flask, the heat always escapes, even if it is exceedingly well insulated, and if it was exceedingly well insulated, it should get enough heat from the sun. However most houses are not exceedingly well insulated, therefore there will be massive heat losses going on if the entire house is heated, at all times.

tweake, Jun 30, 12:07pm
yes agreed its more efficient.
however heating the house is good for the house, not just the people in it. a big part of controlling moisture is from the house being heated.
if we had decent insulated houses, heating costs would be low and we could easily heat the entire house. but unfortunately we just do not build normal efficiency houses let alone high efficiency houses.

"it should get enough heat from the sun."
interesting comment and while a agree whole heartily that they should, those days are disappearing for most people. higher density housing means lack of sun for most houses. the big downside to urban living.