New Self build, Northern Ireland

[Kevan Marshall]

 

Hi,

I am at the stage of planning a self build in Northern Ireland, the bungalow shall be a SIP’s build from Clays, foundations shall be strip foundations and brought up to floor level from sub base with cement screed/selflevelling grout with either PIR insulation or insulated concrete in between, I am hoping to get the house insulated to a very high standard and as near to passive for as cheap as possible, my issue is I stay in Northern Ireland and there are absolutely no grants available for renewables, I would rather spend money on triple glazing and more insulation rather than throw money at expensive heating systems that are overkill for a highlyinsulated house, I shall still need some form of heating mainly for hot water and for when it is cold in winter, I have read that even installing underfloor heating is overkill unless used in conjunction with ASHP as they are generating lower water temperatures, I can install biofuel LPG and conventional radiators but have to be careful not to overheat the property and may only need a few radiators in bathrooms and a couple of large radiators to act as a buffer to help the boiler, has anyone installed a gas or oil boiler in a highly insulated house and how do you find it, I shall also be installing Solar panels and battery system and MVHR, any advice would be greatly appreciated!

Kind regards,

Kevan Marshall.

 

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[JohnMo]

2 hours ago, Kevan Marshall said:

strip foundations

These are quite straightforward, but you will need to think about cold bridges where you meet the SIPs

2 hours ago, Kevan Marshall said:

either PIR insulation or insulated concrete in between

Really need PIR or EPS, 200mm for PIR and 300mm for EPS ideally, little less is ok if not going UFH.

2 hours ago, Kevan Marshall said:

installing underfloor heating is overkill unless used in conjunction with ASHP as they are generating lower water temperatures

UFH is pretty cheap to install, we have it at 300mm centres, think @TerryE is similar. I use an ASHP, so I can get cooling, @TerryE uses a time of use tariff and a pair of Willis heaters.

 

2 hours ago, Kevan Marshall said:

bungalow

 

2 hours ago, Kevan Marshall said:

only need a few radiators in bathrooms and a couple of large radiators

Don't under estimate how little heat moves about in a bungalow, MVHR flow rates are low and don't help distribute.  A heater matrix in the mvhr will help with heating (not cooling), at Passivhaus MVHR flow rates it will distribute 10W/m2 floor area - no more than that.

 

2 hours ago, Kevan Marshall said:

I can install biofuel LPG

I would get a decent boiler with good modulation. UFH helps with boiler over sizing as the floor will buffer the heat.  Last year with boiler with min turn down of 7-8kW, I was able to heat house with little or no overshoot and without boiler stopping once started.  A +0/-0.1 thermostat is your friend and so is thick screed (100mm plus) as it will buffer heat freely. What ever you do you need to consider weather compensation for UFH or radiators or opentherm for radiators, this will give low flow temperatures and limit any likelihood of overshoot of room temps, plus its way cheaper to install than multiple thermostats.

 

Don't do Y or S plan, do X or W plan (or Priority Domestic Hot Water), so you get one flow temp for cylinder heating and another for CH. This will get efficiency from boiler.

 

2 hours ago, Kevan Marshall said:

shall also be installing Solar panels and battery system

For me this makes an ASHP a no brainer, shoulder season all heating is just about free.

[Kevan Marshall]

Hi John,

Was considering using radiators and was advised by warmflow to install rads in bathrooms and a larger radiators in living/kitchen/dining area without thermostat to act as a buffer and place some sort of manifold so water is diverting back to boiler and condensing so it is not running at low heat all the time as oil boilers do not like temperature output being turned right down, I may install underfloor heating at 300mm centres to future proof the bungalow and for aesthetics having no radiators, I shall be installing the cheapest solar panel and battery system to keep my electricity bills down but also I have heard in NI if you install one form of renewable you can install a gas or oil boiler, I shall try and get U-values as low as possible with building a SIPs structure, being as airtight as possible and minimising glazing that opens as my MVHR should help with that, I need to speak to concrete suppliers to ask about insulated concrete and speak to Mannok about PIR insulation to see what’s going to be the cheapest option, I have been in contact with ASHP installers but they cannot give me an estimate of running cost or installation cost but do try and give me the hard sell, my friend who built a conventional house for a customer about three years ago had ASHP and it has broke down already and is costing about 2k - 2.5k a year to heat a 3000 square foot house which was insulated with EPC A rating, to be honest the heating side of things is the most difficult to get sorted and also to get impartial advice, hopefully with advice on here from people such as yourself then I can make a decision of which route I am going down, this may sound very irresponsible but I am looking for the most straightforward solution instead of what my carbon footprint is, I would rather spend money on getting U values down rather than spend tens of thousands on expensive ASHP, also the issue in Northern Ireland is that there are absolutely no grants available for renewable heat sources…

Kind regards,

Kevan.

[Conor]

Don't get a gas boiler. Just don't. Especially lpg.

 

Our 250m² new build total electric bill for a year is about £2k, and that's heating, hot water, washing, cooking, car charging.

 

If you have a limited budget for these kind of things, ditch the batteries and get the ASHP. 

 

I got guys from the North coast to install ours, only took a couple of days and it's been absolutely perfect for three years now. Love it. And remember, can't cool your house with a gas boiler....

Edited yesterday at 16:51 by Conor

[Kevan Marshall]

Hi Conor,

Do you have Solar panels and out of the 2k have you worked out how much it costs you to charge your car?

Kind regards,

Kevan

[JohnMo]

17 minutes ago, Kevan Marshall said:

minimising glazing that opens as my MVHR should help with that,

No it won't, you want opening windows to enable purge ventilation to get rid of excess summer heat

[JohnMo]

18 minutes ago, Kevan Marshall said:

ASHP installers

If you can install a boiler and ASHP is easy.

[JohnMo]

21 minutes ago, Kevan Marshall said:

my friend who built a conventional house for a customer about three years ago had ASHP and it has broke down already and is costing about 2k - 2.5k a year to heat a 3000 square foot house which was insulated with EPC A rating, to be honest the heating side of things is the most difficult to get sorted and also to get impartial advice

We are 200m², currently cooling with ASHP, with solar and battery, we are not paid for any export and ALL electric is costing about 30 to 40p a day. Heat pump efficiency is all about design, the simpler the better. You run 24/7, you have one heating zone, no buffers are needed, no thermostats are needed if run on Weather compensation. A CoP of 4.5 and above is pretty easy to achieve, including DHW heating. The ideal design is, ASHP, 3 port diverter, UFH manifold (no actuators, mixer or pump) UFH loops and a cylinder, interconnected pipes insulated. Cylinder (3m² coil)£1k or less, heat pump shop around £1500 upwards, UFH several hundred pounds.

[Kevan Marshall]

2 minutes ago, JohnMo said:

No it won't, you want opening windows to enable purge ventilation to get rid of excess summer heat

Thanks John, 

I’ll need windows that open in bedrooms and bathrooms for building regs, I shall also have three lift and slide patio doors so every room shall have windows that open where necessary but yes better with the option of being able to open so not to overheat in summer!

[Kevan Marshall]

3 minutes ago, JohnMo said:

We are 200m², currently cooling with ASHP, with solar and battery, we are not paid for any export and ALL electric is costing about 30 to 40p a day. Heat pump efficiency is all about design, the simpler the better. You run 24/7, you have one heating zone, no buffers are needed, no thermostats are needed if run on Weather compensation. A CoP of 4.5 and above is pretty easy to achieve, including DHW heating. The ideal design is, ASHP, 3 port diverter, UFH manifold (no actuators, mixer or pump) UFH loops and a cylinder, interconnected pipes insulated. Cylinder (3m² coil)£1k or less, heat pump shop around £1500 upwards, UFH several hundred pounds.

Thanks John,

I think the house that my mate built had some really poorly installed ASHP, how big is your solar and battery system?

[Stratman]

Re opening windows, does NI have building regs document equivalent to Approved Document O? This may restrict counting some windows' contribution to night time cooling if they are on ground floor as they may not be considered secure.

[JohnMo]

25 minutes ago, Kevan Marshall said:

how big is your solar and battery system?

13.4kWh battery. PV is around 7kWp, but at different angles and plenty of shadow from trees. So really more like a 4kWp system.

[Conor]

1 hour ago, Kevan Marshall said:

Hi Conor,

Do you have Solar panels and out of the 2k have you worked out how much it costs you to charge your car?

Kind regards,

Kevan

Yes. 4.5pkW. no batteries as does not make payback threshold for us. We're on economy 7 and do bulk of our hot water, heating and car charging off peak. Car is quite small, just a leaf that's charged a handful of times a month. Maybe a fifth of the overall consumption. Solar saves us about £1k a year. Cost £6k to install so halfway to payback already.

 

When doing the M&E design five years ago, I calculated our annual bills to be £1200 before car charging. Obviously electricity going from 15p a unit to 25p, has accounted for the higher than expected costs.

Edited yesterday at 18:31 by Conor