Heating System for new build query

sman

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Hi, I am just working out construction drawings for my new build bungalow. I would like to make the house airtight, use increased levels of insulation, and use MHRV to minimise heat loss. I had also planned on putting in underfloor heating in the living areas with rads in the bedrooms. I plan on using solar panels for hot water for showers etc. and then condenser oil burner for heating. My question is, am I wasting money putting in underfloor when I am also paying for extra insulation and MHRV.

Would I be better off putting in aluminium radiators instead of the added expense of underfloor?

One builder I spoke to recommended going with underfloor throughout the whole house and dropping the MHRV as the Electricity costs are too high for this but I think having an airtight house is the best way forward. Anyone aware of the typical running costs of MHRV?

Any opinions welcome… need to make a decision on it fairly quickly and afraid I’ll end up choosing the wrong thing
 
We got our MHRV airtight house done but system not being turned on until the end of this week so costs can't comment on on running. But the whole point really is that you don't need underfloor heating nor radiators. The ventilation system works on its own, backed up by a condensing boiler to boost the whole unit when it is really cold and needed and once you have it on for a while you can turn it off and the heat that it previously kicked out will stay in the house as it is airtight, minimal amount of heat loss, as you will see if you search this forum, no matter what heating system you use, the key is always insulation, the more the better.
 
I've spoken with a couple of plumbers recently on this subject and from what I can glean the best and most efficient system longterm is underfloor heating fed from an oil condenser boiler (the Grant boiler was the one most frequently mentioned), coupled with solar panels tied to the hot-water system.

There seem to be problems with the heat exchanger for asthmatics, though this is based on hearsay, I can see how it would make sense. Ventilation is important, personally I don't like the idea of a 100% sealed house.

As mentioned, insulation is key. 125mm foil-backed high density is the minimum requirement for underfloor and should be well worth the initial cost.
 
Thanks for the replies. decisions decisions to make. hate to spend 8 grand extra on underfloor heating and then have it sitting there unused.

We got our MHRV airtight house done but system not being turned on until the end of this week so costs can't comment on on running. But the whole point really is that you don't need underfloor heating nor radiators. The ventilation system works on its own, backed up by a condensing boiler to boost the whole unit when it is really cold and needed and once you have it on for a while you can turn it off and the heat that it previously kicked out will stay in the house as it is airtight, minimal amount of heat loss, as you will see if you search this forum, no matter what heating system you use, the key is always insulation, the more the better.

Abbica... when you say it is backed up by a condensing boiler. this must be heating either underfloor or rads
 
hate to spend 8 grand extra on underfloor heating and then have it sitting there unused.

The solution to this is to split the house into zones with controls/timers for each zone. I.e. have the bedrooms on one zone timed for night and morning, kitchen/living area on a separate zone, timed accordingly. Its very easy to leave the pipes out for rads when you're building should you decide that they're a better iption down the road.
 
Hi Sman, we have solar panels on the southside roof which will heat up our water, we have the ventilated ducting throughout our airtight house for heating, so no radiators or underfloor, the heat flow goes through the ducting, so say its winter and the water isn't hot enough we turn on the boiler for a bit to give it that extra heat and the same applies for the heat, the boiler heats up the air that will dispel into the house, clean fresh air that is warm, like a car heater so to speak. Don't ask me technical stuff on how it works but its the latest in passive heating. No one, not one builder coming into our house can figure out how it will work, all they say is' 'jaysus, I will have to come back and see how this work'. I think they think we are been conned!!!
 
thanks abbica. i understand now. makes sense i suppose. someone mentioned this to me before at a selfbuild show, but i had assumed it was just an addition to conventional heating. i.e. the pipes carrying hot water to the rads or underfloor are passed through the ducting. I hadnt thought of just having the pipes going through the ducting as the heating source. be very interested to know how you get on with this
 
The solution to this is to split the house into zones with controls/timers for each zone. I.e. have the bedrooms on one zone timed for night and morning, kitchen/living area on a separate zone, timed accordingly. Its very easy to leave the pipes out for rads when you're building should you decide that they're a better iption down the road.

thanks. i understand having the zones alright. just wondering should i put in underfloor at approx 8k extra or is MHRV efficient enough to almost reduce the need to heat the house at all. If it is, i should go for cheapest heating system as it would be rarely used
 
HRV systems are not heating systems from what I have seen. They are ventilation systems which heat the cold air coming in to house with stale warm air that they are removing from the house so that there is little change in the air temperature. They usually take this air from areas such as bathrooms and kitchens which would usually have higher temps due to cooking and steam etc. But you still need to be able to heat your house first unless it is a passive house ( extremely well insulated and air tight house that has no heating system at all).

I would think from the info you have given Abbica that your oil boiler will be coming on most of the time in the winter to heat your house.

I am no expert by the way, it just what I have gathered from reasearching these systems myself.
 
Hi wobs, I know what you mean and I do believe we will have to turn on the oil boiler in the winter almost every evening but because it is a passive airtight house the point is, it need only be on for 1 - 2hrs (I am presuming), as the heat that it throws out will stay in the house, no need to have it on for ages?
 
thanks. i understand having the zones alright. just wondering should i put in underfloor at approx 8k extra or is MHRV efficient enough to almost reduce the need to heat the house at all. If it is, i should go for cheapest heating system as it would be rarely used

as wobs has stated...
the hrv system is not a heat producing source.. what it DOES do is conserves heat already produced by your heating system..

whether or not to go for UFH as compared to rads should be based on other issues
(1) UFH is more economical as it runs at lower temperatures than Rads
(2) some people like having rads to dry towels etc... this is possible with UFH but is an extra cost
(3) UFH is aesthetically more pleasing as you do not see rads under windows.. it also allows you to be more free when laying out a room
(4) UFH generally allows you much more control over your heating system, and thus allows you to conserve energy better.
 
Hi All,
First time poster so bear with me. Planning to build my own house using ICF system to relatively low U-values but maybe not 'passive' standards. However i'm having trouble sourcing heat system info! In addition to HRV I was planning to use UFH down stairs and rads upstairs powered by wood pellet burner. Wise decision?? Also, why is it not advisable to have an open fire in an 'airtight' house?

Thanks in advance
Bov 1
 
ill answer the second question first...
basically because an open fire mean there is a large 200mm diameter hole in your construction... ie the chimney flue. Its pointless building an 'airtight' house and then deliberately putting a large hole in it.

to answer your first question.... what you need to do is work out your heating demand first, before you can specify a heating system. the DEAP software can be used to do this, but if you want a more precise figure get the design put through th phpp software.
Once you know what your demand is, you can then go about sourcing a system to meet this demand.

for example.. two passive houses built in carlow have a small 1.7 kw/hr electric air to air heat poump as their heating source...
 
Hi All,
powered by wood pellet burner. Wise decision??

Don't have personal experience of wood pellet boilers but am in regular conversation with an SEI registered plumber who has told me horror stories about them, including nests of rats in the silo, among other less horrifying tales.

Maybe people who have wood pellet systems can give testament as I am only going on hearsay, though there are probably numerous threads already on the topic.
 
whether or not to go for UFH as compared to rads should be based on other issues
(1) UFH is more economical as it runs at lower temperatures than Rads
(.

syd, have you any stats on that?

UFH has maybe 20 times more water in it than a radiator system. More water = more energy required to heat it.

UFH does run at a lower temperture but for much longer periods as compared to a radiator system, higher running temperture, shorter running time.

UFH has a slow warm up time, not ideal for a cold snap in August when you just want to turn heating on for an hour.
 
God, you lot have me worried now, we don't have any alternative heating source, all we have is the solar panels, HRV system, condensing boiler with the air tight passive house. It is been commissioned by a heating engineer????
 
Hi Abbica,

What airtightness result did you achieve on your blower door test and what insulation u-values did you achieve? You built direct labour, right?
 
syd, have you any stats on that?

UFH has maybe 20 times more water in it than a radiator system. More water = more energy required to heat it.

UFH does run at a lower temperture but for much longer periods as compared to a radiator system, higher running temperture, shorter running time.

UFH has a slow warm up time, not ideal for a cold snap in August when you just want to turn heating on for an hour.

davy, my opinion is based on the premise that the building envelope is of high spec airtight type. Once the heat is generated within the dwelling, then every effort must be made to retain it. A rad systems is much better for a warm up / cool down type set-up.. .UFH is much better, and more economical, for a set-up designed to have a constant temp throughout the dwelling 24 hrs a day. This is the way things are moving to.

yes rads are more responsive, but increased controls over the UFH system and a better spec of construction ie min 120mm pu under UFH in a 75mm screed, can increase the responsivness of UFH.

again, i agree that UFH contains more liquid, but my first point applies here... the temp differentials in UFH should be in the range of 15-40.. .whereas rad systems tend to be about 10 - 70.. less temp differential means less energy required to heat...

abbica... if your house is a 'passive' house then then only heating source you require would be of a very small output... ie 2kw/hr or so... the condensing boiler would be more than enough...
 
Hi Syd,

I would be very interested in looking at stats that compare installation and running costs of both systems.

I always belived we live in an unsuitable climate for UFH/low temp systems. It is more suited to a climate where you are certain that the heating would be on from October to february etc.

I hear alot of people with UFH complain of high fuel bills. I would not install it in my home and would be slow to fit solar panels/heat pumps etc.
 
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