What Heating System?

ShiverinEskimo

Just lodged our plans to our local council and am looking for advice as to what kind of heating system/boiler to opt for.

It's a block-build dormer bungalow. We will have underfloor heating downstairs and radiators upstairs.

Everyone we speak to offers a different opinion so I understand there's no right or wrong system, and all will have benefits but I'm just trying to get a concensus.

Our architect at the moment is leaning towards oil or gas fired boiler. (Gas would require the installation or burial of a large tank as seen here ) I have a friend who swears by his air-source heat-pump and another friend who is going with wood gasification boiler coupled with a HRV system but his house is air-tight, timber frame as opposed to block so not sure if I could get the same level of air-tightness required for such a set up to be suitable.

Other advice I'm open to is whether having rads upstairs is a good idea - would underfloor throughout be more ideal given it would be more suitable for having a boiler running at a low setting more often, than requiring a boost for the rads on top of the slow-burning underfloor heating.

Sorry if I rambled a bit but months after I started thinking about this I'm no closer to knowing what would be best.

BryanF

imho and if it was me building:) get your build designed to circa 15kwh/m2/pYear (15 being the passive house standard) with good design, insulation, Air-tight etc.. you THEN look at several options: In order of my preference:

• a simple timber log burner/boiler with Solar thermal panels.
• the more complicated (but if done correctly grand route) of GSHP, but here's the catch this need a back-up source! and there's electrical consumption.
• there also the thermal store systems, i like this idea but would rather do it on my own house first rather than a clients

I think currently with any of the above MVHR should also be in the mix..

best of luck with it. has your arch mentioned phpp(passive house) or provisional BER?

ShiverinEskimo

Cheers Bryan.

We haven't discussed anything like PHPP. I've insisted throughout the design that I will be aiming for a well-insulated build but am of the impression that with block build it can be more difficult to achieve air-tightness. I will be instructing the builder to build the inner leaf first to allow us to tape the boards to improve it and will be fairly picky when it comes to seating the windows and will opt for triple glazing with a wide cavity section.

Any thoughts on the UFH/Rads vs UFH throughout are welcome.

Outkast_IRE

Underfloor or rads stick to one or the other ,these two types of heating work in two very different ways .

Underfloor creates a nice ambient heat, wheras rads as we all know just give a big blast of heat when needed.

I have installed both types of systems and when a hybird rad/underfloor system is asked for i always advise against it.

With underfloor you get the heating to come on a few hours before you need it in order to heat the slab and the slab to heat the room , with rads you just flick the switch when needed. the underfloor also works at a lower temp than the rads . This is just one example of how the system differs and people can find it hard to set times for the two different systems and often you will find the rooms with rads feel stuffy when they are on compared to the underfloor.
Basically if you do a hybrid system you arent getting the full benefits of either system.
Also imo I would pick oil over lpg , lpg is dearer and can be a prick to get topped up as plenty found out the last 2 winters.

MicktheMan

ShiverinEskimo wrote: »

I've insisted throughout the design that I will be aiming for a well-insulated build but am of the impression that with block build it can be more difficult to achieve air-tightness. I will be instructing the builder to build the inner leaf first to allow us to tape the boards to improve it.

There is no reason that a block build cannot be as airtight as a tf.

Are you taping your insulation boards to achieve airtightness? If yes then (with all due respect) I'd query the person advising.

The airtightness line is the inner face of your external wall (i.e inner face of the internal leaf in a cavity wall).

Your challange to achieve airtightness will be ensuring the dormer roof is airtight and connects to the wall airtight layer without any gaps, that the walls are sealed to the floor, the windows/doors taped properly and don't forget that workmanship will make or break airtightness.

MicktheMan

Hi, just to clarify, taping the insulation boards is a good idea from an insulation effectiveness point of view but will add little to airtightness.

ShiverinEskimo

Sorry lads - the taping of the boards is just to improve the insulation and reduce/remove airflow around the boards - not the air tightness.

I always thought that block build is quite difficult to ensure air tightness - an incorrect assumption I suppose. This is my first time building

sydthebeat

ShiverinEskimo wrote: »

I always thought that block build is quite difficult to ensure air tightness - an incorrect assumption I suppose. This is my first time building

the quality control of a timber frame build build can be easily measured as its very much off site factory based. Therefore expected air tightness results can be given with some sense of reality.

on a block build the air tightness result is much much more dependent on the knowledge, skill and interest levels of all the tradesmen working on it. therefore its much harder to estimate what level you are building to. there is however a lot of information available as to how best garnish results. The majority of passive houses in ireland are block builds, so that should tell you enough.
Proper informed detailing, attention to that detail and adequate budgetary support can allow you reach whatever air tightness result you wish.

BryanF

ShiverinEskimo wrote: »

Cheers Bryan.

We haven't discussed anything like PHPP. I've insisted throughout the design that I will be aiming for a well-insulated build but am of the impression that with block build it can be more difficult to achieve air-tightness. I will be instructing the builder to build the inner leaf first to allow us to tape the boards to improve it and will be fairly picky when it comes to seating the windows and will opt for triple glazing with a wide cavity section.

Any thoughts on the UFH/Rads vs UFH throughout are welcome.

that's not true re air-tightness.
but why block?
If it was me, at the stage your at: I'd already have worked out in how to maximise insulation, air-tightness and minimised the thermal bridging.. with the heat requirements, I'd have minimised the need & amount of rads and removed the need for UFH altogether.

UFH is a personal choice by many who have lived in crappy, drafty, hard to heat homes all their lives (myself included).. we now have the know how and case studies that show we can build practically zero energy in use homes and that's what id be trying to achieve before commenting on UFH/Rads:)

ShiverinEskimo

Reason we went for block was because we were advised there were savings to be made because of the cost of brickies and blocks of late has dropped compared to Timber frames. I also was brought up in an old draughty noisy house and wanted to have a good solid, relatively sound-proofed house both from outside and also between floors. The block build allows me 100mm of concrete slabbing between floors and since the house will be right at the roadside (few metres back only) I reckon the block build coupled with triple glazed front windows (if not all over) will ensure a nice, peaceful house.

Our architect also seems to be a fan of block build too and so was always leaning towards that in the design stage. He's unconvinced by some of the newer type heating systems like ground source and air source because of the rising ESB charges - reckons what you save on fuel, you'll spend on leccy. Hence the thread really - I'm hearing different opinions from pros and punters alike.

BryanF

http://www.greenbuildingstore.co.uk/page--passivhaus-diaries.html i find this a good read on a good block build

and they went with gas:eek: but wait till you see how much they needed:)

bbam

I'm not a supplier or professional but we finished our build two years ago..

We got advice from a friend who is in the insulation/building business who knew we weren't doing any buisness with, so I feel he gave good impartial advice..

The key point isnt in what heating system but how to mimimise the requirment for a heatinmig system to be on at all...

He explained that the important aspects were a combination of airtight and insulation... there is no point in being surrounded in insulation but air passing through will bring out the heat anyway...

External block walls should be plastered on both sides to prevent air infiltration..
Detailing round doors and windows needs to be inspected to ensure they are correct and not left to blocklayers and window companies..

We both pumped the cavity and insulated internally with 50mm high density board..

We spoke about underflor and the key seems to be the low level of radiated heat is easily offset by any problems in airtightness of the build.. Absolute control of the ventilation with these systems is a must.. This is a system that raises the temperature slowly and if even small ammounts of heat are being lost then the heat will fail to build up.

In the end we went for a high efficiency oil boiler and large boiler stove.. For the last two years we have burned less than a tank of oil each year and about 2 ton of timber.. We were priced for geothermal & under floor but it would have been an additional €16-€18K plus higher ESB costs...

ShiverinEskimo

That's great information bbam - thanks a million.

From the sounds of things I'm going to really need to hammer home the air-tightness factor with my Architect who will also be project-managing the build so I'll be making sure he is making sure that all seals etc. are done to the appropriate standard.

I'm assuming I should be pushing for a HRV system then too if the air-tight route is on the cards? I assume this won't affect my plans too much or would suitable space for ducting etc. have had to be allowed for prior to this in the plans?

(Note: I would ask my Architect these questions but he's off on hols at the moment.)

BryanF

http://www.passivehouseacademy.com/downloads/New-Build-Passive-House-Guidlines.pdf
have a read of this.
Bbam makes some good points here re ins & air-tightness, but why you'd build in block and then dryline is beyond me, just go with a wider cavity.. and 'less than tank of oil (wahat are we talking here 1000L?) + 2 ton of timber' could still cost you over a grand... so i wonder could more be done in your new build to reduce this energy cost further...

re: duct for MVHR, yes they really should have been considered prior to submitting planning, but that does not mean it is to late! where there's a will there's a way:) . because of your busy road, having a system that will filter the incoming air would help reduce pollutants/ car fumes.

bbam

BryanF wrote: »

so i wonder could more be done in your new build to reduce this energy cost further...

Indeed it could have..
If budget haddn't been so tight I'd have widened the cavity to allow more bead to be pumped in, and possibly gone with external insulation rather than dry-lining.. However wider cavity would have pushed up the cost of foundations and the build..
External insulation... I just wasn't sold on it at the time , and it was working out quite expensive...I'd probably look better into it if I was building again...

Our timber is free to cut myself and 3/4 tank of oil is fine for me... I could burn more timber if I needed to cut back oil consumption but I just hate the chainsaw.

You also need to look at payback... Unless you were to acheive a full passive house build then heating would still be a cost..
We weren't going for the full passive house so I could never see us getting under say 1/2 tank of oil consumption a year... the extra cost of getting to that wouldn't have been worth it IMHO.

AMG86

Go as near as you can to Passive. The cheapest energy is the energy is that is not used. Insulate well, build tight and ventilate is the way forward. On site workmanship is key to achieving a good level of air tightness. Forget about the 10 m³/hr/m² mentioned in the Guidelines. Go for best practice of 3 m³/hr/m² or better. With 5 m³/hr/m² or less a HRV system will reduce heating costs and add to comfort levels. See http://www.seai.ie/Renewables/, http://www.mosart.ie/, http://www.proair.ie/index.php?option=com_content&task=view&id=70&Itemid=220 and http://www.passiv.de and many more.