Cooling to Complement Radiator Central Heating in New Build Design

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#3027651 26-Jan-2023 19:01

mattenz:

Decal:

Have you looked at the cooling options from your water to air heatpump?

https://www.centralheating.co.nz/central-heating-design/radiant-cooling/

Not one mention of the major concern with those types of systems, which is where the moisture condenses.

When you run a chilled beam/ceiling you have a condensate sensor on the cooling element. If you have condensate it will rain.

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MikeAqua

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#3027732 27-Jan-2023 08:49

timmmay:

Have you ever had ducted central heating in a house you've owned / stayed in? It might be worth trying to experience that to reduce costs a bit. But if you want radiators, sure, it's your money.

This summer we're finding cooling of bedrooms super valuable, it's getting hotter ever year.

I won't have the roof space for ducting. The roof will be a mono pitch skillet to maximise both sunlight and rainfall collection and minimise guttering (fire hazard).

I already have the radiators and they actually weren't that expensive.

The house won't actually need a lot of kW of heating because it' will be built to be very efficient and make good use of the sun in winter.

If I had more roof space, then a combined ducted heat-pump and heat recovery ventilation system would have been the go. As you note the good ducted systems are quiet and the house will be designed to allow air to move freely so temperature will even out

Mike

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#3027743 27-Jan-2023 09:11

High wall units with a single outdoor might be the best option for cooling then. Just beware if you think you'll use them for heating as well, if you have part of the house that will need heating and part that will need cooling they need separate outdoor units. For example, in my house the west facing kitchen gets a LOT of sun and gets warm in the afternoon all year round and need cooling, whereas the bedrooms and living area may need heating.

mdf

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#3027767 27-Jan-2023 10:01

MikeAqua:

I won't have the roof space for ducting. The roof will be a mono pitch skillet to maximise both sunlight and rainfall collection and minimise guttering (fire hazard).

I already have the radiators and they actually weren't that expensive.

The house won't actually need a lot of kW of heating because it' will be built to be very efficient and make good use of the sun in winter.

If I had more roof space, then a combined ducted heat-pump and heat recovery ventilation system would have been the go. As you note the good ducted systems are quiet and the house will be designed to allow air to move freely so temperature will even out

I ❤️ skillion roofs. Both our old and current place have them, albeit some criminal has added a false ceiling to hide the skillion roof in the current place - it is still there and plans are in place to reinstate it. I suspect you're on top of this already, but at our old place, installing skylights in the roof made a massive difference in terms of passive cooling ventilation. Lets the hot air rise right out but also encourages a through breeze so if we opened the windows on the non-sunny side of the house, was very pleasant. That might not be compatible with your solar panelling though.

And the sound of rain on a skylight is genuinely one of my favourite things.

timmmay

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#3027795 27-Jan-2023 11:00

Wouldn't a skylight make the place significantly colder in winter?

MikeAqua

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#3027823 27-Jan-2023 12:42

timmmay:

Wouldn't a skylight make the place significantly colder in winter?

Double glazed and non-opening with a honey-comb type blind (remotely operated). It will have reasonable R-value and the areas involved aren't that large.

Mike

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#3027831 27-Jan-2023 12:54

mdf:

I suspect you're on top of this already, but at our old place, installing skylights in the roof made a massive difference in terms of passive cooling ventilation. Lets the hot air rise right out but also encourages a through breeze so if we opened the windows on the non-sunny side of the house, was very pleasant. That might not be compatible with your solar panelling though.

And the sound of rain on a skylight is genuinely one of my favourite things.

I'll have gaps in the solar arrays where the skylights are but I didn't want openable skylights, from an R&M perspective and because of the risk of damage to the blinds.

I have openable top-light windows on the North side (1.5 stud height) and openable low-level windows on the south side. If it gets too hot I'll be able to get some cross-flow going. It's not ideal but it's the best I could do with the geometry and the prevalent Northerly winds during hot weather.

I wanted the tall side on the south for diffuse natural light during summer, without heat (blinds) for winter. I've been in a couple of houses in Marlborough with this arrangement and it works well. The trees and eaves will block the sun on the North side during summer but not during winter.

Mike

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#3027841 27-Jan-2023 13:07

MikeAqua:

I'll have gaps in the solar arrays where the skylights are but I didn't want openable skylights, from an R&M perspective and because of the risk of damage to the blinds.

I have openable top-light windows on the North side (1.5 stud height) and openable low-level windows on the south side. If it gets too hot I'll be able to get some cross-flow going. It's not ideal but it's the best I could do with the geometry and the prevalent Northerly winds during hot weather.

I wanted the tall side on the south for diffuse natural light during summer, without heat (blinds) for winter. I've been in a couple of houses in Marlborough with this arrangement and it works well. The trees and eaves will block the sun on the North side during summer but not during winter.

Sounds super sensible to me! Cross flow is an awesome thing to take advantage of, if you can swing it.

Given all that, and that your main heat pump/AC option would appear to be in-wall units, my only other question would be whether there is any benefit in installing the heat pumps during the initial build, or build now and live in it for a bit, then retrofit the heat pumps later if necessary? Then you can dial up/down your specs as required (e.g., this room is warmer than expected, go bigger, but that one is cooler so not necessary). You could add the wiring now (and I find outside sockets super useful anyway) and maybe a bit of blocking, but other than that, are there any other advantages about installing an in-wall unit during the initial build c.f. retrofitting in a year?

nickb800

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#3027855 27-Jan-2023 13:24

Can you get away with some good ol fashioned ceiling fans? Would help to avoid the capital cost of two heating systems.

We have ceiling fans for summer cooling, find they have low capital cost, minimal running cost, and work really well (as long as you're underneath them)

Kim587

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#3027880 27-Jan-2023 14:25

mdf:

MikeAqua:

I'll have gaps in the solar arrays where the skylights are but I didn't want openable skylights, from an R&M perspective and because of the risk of damage to the blinds.

I have openable top-light windows on the North side (1.5 stud height) and openable low-level windows on the south side. If it gets too hot I'll be able to get some cross-flow going. It's not ideal but it's the best I could do with the geometry and the prevalent Northerly winds during hot weather.

I wanted the tall side on the south for diffuse natural light during summer, without heat (blinds) for winter. I've been in a couple of houses in Marlborough with this arrangement and it works well. The trees and eaves will block the sun on the North side during summer but not during winter.

Sounds super sensible to me! Cross flow is an awesome thing to take advantage of, if you can swing it.

Given all that, and that your main heat pump/AC option would appear to be in-wall units, my only other question would be whether there is any benefit in installing the heat pumps during the initial build, or build now and live in it for a bit, then retrofit the heat pumps later if necessary? Then you can dial up/down your specs as required (e.g., this room is warmer than expected, go bigger, but that one is cooler so not necessary). You could add the wiring now (and I find outside sockets super useful anyway) and maybe a bit of blocking, but other than that, are there any other advantages about installing an in-wall unit during the initial build c.f. retrofitting in a year?

Its a fair point that waiting until later to install the heat pumps would give a better idea of what specs you need. Playing devil's advocate, the two advantages I can think of for putting them in during the build are:

1. Much easier to plumb the units into the exact locations you want them before the GIB goes in. Especially if the ideal place for the internal unit is on an internal wall and the external unit is some distance away. Possibly not an issue if the internal unit is going to be mounted on an external wall and you are happy for the outdoor unit to go 'back to back' on the opposite side of the wall.

2. If you are maxing out your budget, it can sometimes be easier to include things in the finance package for the build than to have to find a way to pay for them separately later. You might also get better trade pricing through your builder.

This sounds like it is going to be a pretty amazing project! Good luck with everything! Is this your first time building?

timmmay

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#3027890 27-Jan-2023 14:48

Cooling needs smaller heat pumps in most rooms than heating, in my experience. In winter it might be zero degrees outside, and you're trying to get your house to 20 degrees, so a large change. With cooling you tend to want to drop it a few degrees.

Re skylight, double glazing is still a lot less insulation than two pieces of wood and pink batts. If it were me I'd go for triple, or not do the skylight.

tweake

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#3027935 27-Jan-2023 16:10

MikeAqua:

I'll have gaps in the solar arrays where the skylights are but I didn't want openable skylights, from an R&M perspective and because of the risk of damage to the blinds.

I have openable top-light windows on the North side (1.5 stud height) and openable low-level windows on the south side. If it gets too hot I'll be able to get some cross-flow going. It's not ideal but it's the best I could do with the geometry and the prevalent Northerly winds during hot weather.

I wanted the tall side on the south for diffuse natural light during summer, without heat (blinds) for winter. I've been in a couple of houses in Marlborough with this arrangement and it works well. The trees and eaves will block the sun on the North side during summer but not during winter.

if your going to go that route then don't bother with cooling. everything your doing is working against using a cooling system. if your want good active cooling then you need to build the house for that.

tweake

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#3027944 27-Jan-2023 16:18

timmmay:

Cooling needs smaller heat pumps in most rooms than heating, in my experience. In winter it might be zero degrees outside, and you're trying to get your house to 20 degrees, so a large change. With cooling you tend to want to drop it a few degrees.

Re skylight, double glazing is still a lot less insulation than two pieces of wood and pink batts. If it were me I'd go for triple, or not do the skylight.

keep in mind that a lot of heat pumps have more heating output than cooling.

skylights are not to bad insulation wise provided its factored into the design. simply because you make up for it by reducing window size. sunlight side of things is a different story.

however skylights are a major source of leaks.

Handle9

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#3027947 27-Jan-2023 16:19

tweake:
if your want good active cooling then you need to build the house for that.

Nah, you just need enough capacity. It’ll be expensive to run but you can overcome a lot with enough kW.

Handle9

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#3027952 27-Jan-2023 16:44

nickb800: Can you get away with some good ol fashioned ceiling fans? Would help to avoid the capital cost of two heating systems.

We have ceiling fans for summer cooling, find they have low capital cost, minimal running cost, and work really well (as long as you're underneath them)

Ceiling fans make a big difference and in my experience are effective up to 30 degrees. I’ve just installed them through my house which has ducted units.

If you are buying ceiling fans modern DC fans are much quieter, cheaper to run and more convenient than old school AC fans.

Saying that I tolerate heat now that I’ve been in the Middle East for over 4 years so take 30 degrees with a grain of salt. I’m freezing today and it’s 17 degrees outside.

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