Cooling to Complement Radiator Central Heating in New Build Design

Forums › Home Workshop DIY › Cooling to Complement Radiator Central Heating in New Build Design

1 | 2 | 3 | 4

Handle9

11386 posts

Uber Geek

Trusted

Lifetime subscriber

#3029115 30-Jan-2023 01:50

You’re over thinking it. It’s a house. Mode control for the plant is manual as it won’t be used for a fair chunk of the year and if you want to change it over you do that.

If you are talking about 2 or 4 pipe fan coil with modulating valves you aren’t talking about a hydronic unit. It’s a different thing. You are using different temperature water and you can actually get good control.

Even on really large systems (multiple MW of chilled water) you don’t predict demand unless you have very specific use cases. Demand comes on, you stage the plant. Demand isn’t usually 0-100% instantly, it comes in gradually as the spaces deviate from setpoint. If you have a specific use case where that happens, like an office building, you use a time schedule to bring the plant on. Even then you only bring in the first stage of the plant and then let it stage if it can’t meet setpoint.

For heating applications you have a high temperature hot water coil or a low temperature hot water coil. Doing a setpoint reset is pointless with such small plant, you’ll just end up in a constantly dynamic system and have plant failures.

It’s really not rocket science.

mattwnz

20141 posts

Uber Geek

#3029116 30-Jan-2023 02:01

MikeAqua:

Designing a new house and have focussed so far on the heating side, which will be radiators. The last two weeks have reminded me that we use active cooling sporadically from November to March. Lets say it's 40 days per year with current climate conditions. Maybe more in El Nino years.

So we'll need a cooling system too. I'll be using shading and air flow to an extent to minimise heating of the house. But ... we're in Marlborough. When the NW blows, we'll need an active cooling system.

I could chuck in some heat pumps. They won't need to be high end just to cool. Would it matter if they're only run sporadically?

There are ceiling fans.

What else is there?

Edit: I forgot to add there will be lots and lots of solar panels.

As a designer of houses, IMO the first thing to look at is designing the house for passive solar heat gain. eg free heating from the sun which is stored in a thermal such as concrete floor slab. Then superspec the insulation. I amazed that people spend all this money of heating and cooling system, yet only build to the minimum building standard for insulation because that is what franchise builders they are using normally builds their off the plan houses.

tweake

2391 posts

Uber Geek

#3029219 30-Jan-2023 09:46

mattwnz:

As a designer of houses, IMO the first thing to look at is designing the house for passive solar heat gain. eg free heating from the sun which is stored in a thermal such as concrete floor slab. Then superspec the insulation. I amazed that people spend all this money of heating and cooling system, yet only build to the minimum building standard for insulation because that is what franchise builders they are using normally builds their off the plan houses.

agree but people put way to much focus on passive solar gain. typical issue is solar gain at the expense of insulation (ie lack of insulation). the solar gain is over done resulting in a very hot house in summer and a cold house any time the sun is not out. one of the big issues is lack of control. in europe you can get external shutters which you can lower to reduce the solar gain. also keep in mind that most solar gain is guess work because almost no one does the proper modelling.

its worth remembering that the new insulation rules only get you to minimum required as per other countries, for the climate. current rules could be up to half as much. so the new rules are not great, you can go better.

timmmay

20574 posts

Uber Geek

Trusted

Lifetime subscriber

#3029223 30-Jan-2023 09:58

We have an old weatherboard house with fairly large windows, it get very hot when it's sunny. I've also noticed the weatherboards get up to about 55 degrees C on the outside, but only about 22C on the inside. I hope the building standards have a gap to allow ventilation now, ours has no gap between the weatherboard and insulation / framing. All we can do is use air conditioning.

tweake

2391 posts

Uber Geek

#3029227 30-Jan-2023 10:15

timmmay:

We have an old weatherboard house with fairly large windows, it get very hot when it's sunny. I've also noticed the weatherboards get up to about 55 degrees C on the outside, but only about 22C on the inside. I hope the building standards have a gap to allow ventilation now, ours has no gap between the weatherboard and insulation / framing. All we can do is use air conditioning.

modern walls have a gap behind the cladding for ventilation. primarily to remove evaporate water and vent moisture. not sure on the effect of heating. the airflow is not big and nothing really stopping the heat radiating.

but i think your temp measurements speak volumes. 55c on outside wall but only 22c on the inside, but still a hot house. thats the effect of windows. most modern designs have way more glass than the old homes. if the house is well insulated, the need for solar gain is small, which means you can have smaller windows which improves insulation and reduces cost.

MikeAqua

7773 posts

Uber Geek

#3029842 31-Jan-2023 08:51

mdf:

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?

That's an option. I could add the wiring and presumably some conduit for the pipes. I don't want heat pump installer, hacking through my carefully sealed building.

Mike

MikeAqua

7773 posts

Uber Geek

#3029843 31-Jan-2023 08:55

Decal:

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

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

I haven't, I'll look into it. It's completely feasible to run the A2W heat pump in cooling mode.

Mike

Equinox IT

Cloud spending continues to surge globally, but most organisations haven’t made the changes necessary to maximise the value and cost-efficiency benefits of their cloud investments. Download the whitepaper From Overspend to Advantage now.

MikeAqua

7773 posts

Uber Geek

#3029844 31-Jan-2023 08:57

timmmay:

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.

It's double glazing plus a blind with good thermal insulation, inside a track. And we are4 talking about relatively small area I think it will be OK.

Mike

MikeAqua

7773 posts

Uber Geek

#3029846 31-Jan-2023 08:59

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)

I can. We'd need to add them before the ceiling is clad, but it's possible.

Mike

MikeAqua

7773 posts

Uber Geek

#3029879 31-Jan-2023 10:07

mattwnz:

As a designer of houses, IMO the first thing to look at is designing the house for passive solar heat gain. eg free heating from the sun which is stored in a thermal such as concrete floor slab. Then superspec the insulation. I amazed that people spend all this money of heating and cooling system, yet only build to the minimum building standard for insulation because that is what franchise builders they are using normally builds their off the plan houses.

We are doing:

140mm framing, with very high R-value insulation;
Well insulated floor;
Well-sealed double/triple-glazed, thermally-broken, joinery;
Deepish slillet roof, with plenty of insulation and an insulating roof underlay (if I can find one). The ventilation system is a genuine heat recovery one, with a summer bypass which will draw air from the coolest part of the southern side of the building. I'm designing internal doors etc to allow airflow around the house so that there is net distribution of warmth from the sunnier/hotter rooms (lounge/living) to the cooler rooms.

We'll make use of thermal gain in winter but not summer - unless I've stuffed up the eave-lengths on the northern side!

Mike

tweake

2391 posts

Uber Geek

#3029912 31-Jan-2023 11:47

MikeAqua:

We are doing:

140mm framing, with very high R-value insulation;
Well insulated floor;
Well-sealed double/triple-glazed, thermally-broken, joinery;
Deepish slillet roof, with plenty of insulation and an insulating roof underlay (if I can find one). The ventilation system is a genuine heat recovery one, with a summer bypass which will draw air from the coolest part of the southern side of the building. I'm designing internal doors etc to allow airflow around the house so that there is net distribution of warmth from the sunnier/hotter rooms (lounge/living) to the cooler rooms.
We'll make use of thermal gain in winter but not summer - unless I've stuffed up the eave-lengths on the northern side!

the critical thing you havn't mentioned is wall to window ratio. its the single biggest factor in insulation. 140mm insulation could easily be worse than 90mm insulation due to size of windows.

also have to be aware of the design tactic of trying to make up for lack of insulation by increasing it in other areas. that can work ok if the house is one big room, but you tend to run into issues with one room that gets a lot hotter/colder than the others. again typically because of window sizing.

not sure where you are, but 140mm insulation is not considered all that high. thats closer to normal especially for south island.

eave length and reflectiveness is what they typically stuff up for solar gain. especially with a mono pitch roof. its well worth while adding something so you can add sails etc for extra shade. keep in mind if you have decent insulation there is little need for solar gain in the first place. as there is less need you don't need such big windows which reduces cost and increases insulation.

if your going to run heat recovery ventilation, then your never going to want to have windows open. that also means you can use cheaper non-opening windows. the idea of having windows/doors open to cool the house down goes right out the window. however it nice to have a comfy seat with a book and coffee by an open window. you can use the ventilation system as your bath fans. as its always on it means nice dry bathrooms and saves having to buy/wire extra fans.

also you may need to think about makeup air for the range hood. either a boost system on the hrv or a separate inlet by the stove. depending on range hood size.

timmmay

20574 posts

Uber Geek

Trusted

Lifetime subscriber

#3029942 31-Jan-2023 13:21

Windows are good for fire escapes.

tweake

2391 posts

Uber Geek

#3029944 31-Jan-2023 13:35

timmmay:

Windows are good for fire escapes.

yes, i highly recommend an opening window in bedrooms for a fire escape. not sure on NZ rules but usa, canada etc its a legal requirement.

MikeAqua

7773 posts

Uber Geek

#3029966 31-Jan-2023 14:56

tweake:

not sure where you are, but 140mm insulation is not considered all that high. thats closer to normal especially for south island.

eave length and reflectiveness is what they typically stuff up for solar gain. especially with a mono pitch roof. its well worth while adding something so you can add sails etc for extra shade. keep in mind if you have decent insulation there is little need for solar gain in the first place. as there is less need you don't need such big windows which reduces cost and increases insulation.

if your going to run heat recovery ventilation, then your never going to want to have windows open. that also means you can use cheaper non-opening windows. the idea of having windows/doors open to cool the house down goes right out the window. however it nice to have a comfy seat with a book and coffee by an open window. you can use the ventilation system as your bath fans. as its always on it means nice dry bathrooms and saves having to buy/wire extra fans.

also you may need to think about makeup air for the range hood. either a boost system on the hrv or a separate inlet by the stove. depending on range hood size.

The house site is in the Wairau Valley near Blenheim.

Every other house I've lived in has 90mm framing so 140mm is a ~50% increase over what I've experienced before. At 140mm wooden framing we will be at R6 vs R3.96 for 90mm (manufacturer's ratings). That without any RE allowance for the cavity barrier.

Solar gain: we're planting deciduous tree to the North of the house. I'll buy bare root stock the winter before the start of the project and ridge plant them on site. They will be ~3m high when I move them to their final locations the winter after the landscaping is finished. So, we'll have shade to about 3/4 of window height. The roof will be 75% covered in solar panels, which will cut down on gain via the roof (shading and wind ducting). I think we'll be OK.

We had a heat recovery ventilation on our house in Nelson. We frequently open the windows and had no issues. It still did a nice job of spreading heat evenly around the house. It wasn't even a well-sealed house or double glazed. Ideally you want a fully sealed house with hrv, but if you have 'leakage' you just need more energy input. I'm not trying to build to any particular efficiency standard (except the building code).

We will have a lot of windows to the North. The big exterior glazing elements (slide-stack doors) will be high quality triple glazing. The smaller windows may only be double glazed. I realise big areas of glass will reduce the overall effectiveness of insulation. The reason I bought the site in 1999 was the spectacular views of the Richmond Mountain range to the North. So we're trading off some efficiency for lifestyle. We will have good floor to ceiling blind systems, which will limit losses.

Mike

tweake

2391 posts

Uber Geek

#3029972 31-Jan-2023 15:20

MikeAqua:

The house site is in the Wairau Valley near Blenheim.

Every other house I've lived in has 90mm framing so 140mm is a ~50% increase over what I've experienced before. At 140mm wooden framing we will be at R6 vs R3.96 for 90mm (manufacturer's ratings). That without any RE allowance for the cavity barrier.

Solar gain: we're planting deciduous tree to the North of the house. I'll buy bare root stock the winter before the start of the project and ridge plant them on site. They will be ~3m high when I move them to their final locations the winter after the landscaping is finished. So, we'll have shade to about 3/4 of window height. The roof will be 75% covered in solar panels, which will cut down on gain via the roof (shading and wind ducting). I think we'll be OK.

We had a heat recovery ventilation on our house in Nelson. We frequently open the windows and had no issues. It still did a nice job of spreading heat evenly around the house. It wasn't even a well-sealed house or double glazed. Ideally you want a fully sealed house with hrv, but if you have 'leakage' you just need more energy input. I'm not trying to build to any particular efficiency standard (except the building code).

We will have a lot of windows to the North. The big exterior glazing elements (slide-stack doors) will be high quality triple glazing. The smaller windows may only be double glazed. I realise big areas of glass will reduce the overall effectiveness of insulation. The reason I bought the site in 1999 was the spectacular views of the Richmond Mountain range to the North. So we're trading off some efficiency for lifestyle. We will have good floor to ceiling blind systems, which will limit losses.

i'll have to look up the specs for the location. however keep in mind that 90mm insulation is about 50% of normal depending on area. thats simply due to nz incredibly poor insulation standards. so yes 140mm will be a big increase for a kiwi but it only gets you to whats normal for everyone else.

the triple panes is a big improvement but again size can remove most of that gain. all good to maximise those wonderful views but it may mean some good design work to enable good insulation as well.

there is a house that was in the news where they had huge big windows for the views, but the rest of the house had minimum windows. they also had a good outdoor area that the glass doors opened onto, that was under a large overhang. it gave an excellent feel of in/out flow without sacrificing insulation. the overhang kept the sun/rain off and made a good outdoor space. really well designed.

with HRV's you need a fairly tight house for it to be worth while. about 5ach, tho some pro's recommend max of 2ach. opening windows/doors etc removes all advantages of using an HRV. you might as well not bother and save the money. theres simply no advantages, apart from keeping the sales person happy, in having an HRV in air leaky homes. even if its an air tight home thats made air leaky by opening windows and doors.

the other thing is if your running ducts for ventilation, add a heat pump to it. that solves your cooling issue.

note: i assume your talking HRV as in its a balanced ventilation system, not HRV the company which typically does positive pressure ventilation systems. huge difference in price and function.

1 | 2 | 3 | 4