Heat Recovery Ventillation System

paddyblue

I've just started to build my house - (Detached, two storey dormer, block walls) & with all of the current hype surrounding energy rating i've done quite a bit of enquiring into different energy saving systems etc & their relative worth. But i seem to have more questions than answers after all of this.

1) Wood Pellet Boilers - Apparently there is no real advantage to having these as they are not regulated so Energy Assesors can't give points for these. I've heard that a gas heating system will score you more points?? This doesn't sound right to me & i would be very reluctant to spend big on a wood pellet boiler if that is the case.

2) Heat Ventillation Recovery Systems - I've gotten numerous quotes for this and they seem extremely expensive (8-10K). I know they replace air vents which will score highly in energy savings (reduced consumption of fuel for heating) but is there real value to be obtained from this? Will i recover these costs in the selling price? Is it the case that if i don't have this system installed i will struggle to sell my home in what is increasingly becoming a buyers market? Anyone know of good offers at the moment on the market for block wall construction?

3) Structural Air Tightness - One supplier of the Heat Recovery Systems i spoke to told me that they are pretty much useless if i don't achieve a good 'structural air tightness' in my home. According to him i would need to install draught strips at doors & windows, wrap the 1st floor timber joists & install a breathable membrane in the 1st floor ceiling - at the very least - to make the Heat Recovery System work effectively. This man's company didn't supply any of these so i have to assume his opinion was unbiased. Are such measures so essential with HRV systems and if so are there any other measures that can be done that will improve 'air tightness' (preferably measures that don't come with large cost implications)

4) What are the most effective systems for achieving a good Energy Rating - B or higher (taking cost into consideration)

5) Finally - Any good websites that offer sound, unbiased advice on how to achieve an effective energy rating?

I don't plan on living in the house but selling/renting. So my main objective is to build to a satisfactory rating so that i can sell in near future if required - but also to do this as cheaply as practically possible (ie not instal lsystems with high cost/low reward ratio)

Any advice on any of my queries will be appreciated

Villain

I have looked at HRV systems as I wanted to implement one in my build, however now that I am going for a standard block cavity construction I'm not sure I will achieve the air tightness required.

I think the best way to go is aim for a HRV system make everything as air tight as possible and then get a blow test done and decide where to go from there.

BTW the quote of 8-10k seems a little high but that depends on the size of your house, I got quoted 6 -7k for a 2,500 sq ft house. AFAIK an open fireplace is a no no if you want a HRV to work well

sunnysoutheast

One factor in this is that you MUST have ventilation of some description, so you can go for a) mechanical HRV b) passive stack ventilation c) trickle vents on windows or d) wall vents.

I have no experience of b). I have only bad experiences of c) and d).

We have a new block-built house with HRV, we also over-specced the insulation. We were careful, but not forensic, on detailing around openings etc.

Having lived in our new house over the winter, my view now is that I would never build or live in a house without HRV. I'd probably do a few things differently but this is not one of them. Many higher-end builds now include HRV in their spec.

We thought about getting an air tightness test - but I wasn't convinced by the people we spoke to, waste of money IMHO. I've spent maybe €50 on silicon to seal around all opes and draughtproofing strips for loft hatches etc - most of it is common sense. Our gas bill for heating and hot water, for a 450m2 house, was €111 for Nov and Dec - about a tenner a week.

Paddyblue - I'd think HRV would be a good selling point. So would loads of CAT5e all over the place!

SSE

ircoha

Some thoughts on the above in the attachments, they are courtesy of a contact in Roadstone so Concrete built is better built.....:D

muffler

Just to remind people that the issue of wood pellet burners is not up for discussion in this forum. Read the charter and posts accordingly as it will save us all a whole heap of trouble.

sinnerboy

PK . if you would be so kind as to post them publicly - they would benefit a lot of people

muffler

sinnerboy wrote: »

PK . if you would be so kind as to post them publicly - they would benefit a lot of people

He can advertise in the yellow pages if he wishes but he wont do it here.

250882

I want to be very careful how I word this as this is just my preliminary research into the subject so feel free to correct me if your in the know.

There are only 2 options with air tightness:
none or
as fully air tight as possible

The standard house to current regs gets an air change rate of about 12 - 20 per hour
new regs SEEM to be aiming for 4
95% of all houses built in Germany today are air tight (their regs state max 3 air changes per hour)
There will be a huge saving in fuel costs (50%+ the fuel?) because there wont be cold air draughts flowing into your house to replace the hot air as it rises and leaves through holes in the structure. This is the reason that a HRV system is only effective on a sealed building, there is no point using it if you are only recovering heat from a small percentage of the air leaving the house.

If you do a half-arsed job of air tightness, any gaps that you leave in the envelope WILL attract all the moisture laden air to those areas and cause localised mould, damp and toxic spores very quickly. In the traditional building system this moisture laden air is released by the draughts caused by room vents.
An air tightness test is necessary, its not just to measure how much air is leaving the building envelope but also where its leaving. It is very important to identify these points and that the correct sealants, membranes and tapes are used. There is no point going around the house with a smoke pen and sealing the gaps with masking tape or silicone as it may perish and wont last long.

Feel free to correct me on any of the above or remove if you think I'm scaremongering

marielle

250882 wrote: »

I want to be very careful how I word this as this is just my preliminary research into the subject so feel free to correct me if your in the know.

There are only 2 options with air tightness:
none or
as fully air tight as possible

The standard house to current regs gets an air change rate of about 12 - 20 per hour
new regs SEEM to be aiming for 4
95% of all houses built in Germany today are air tight (their regs state max 3 air changes per hour)
There will be a huge saving in fuel costs (50%+ the fuel?) because there wont be cold air draughts flowing into your house to replace the hot air as it rises and leaves through holes in the structure. This is the reason that a HRV system is only effective on a sealed building, there is no point using it if you are only recovering heat from a small percentage of the air leaving the house.

If you do a half-arsed job of air tightness, any gaps that you leave in the envelope WILL attract all the moisture laden air to those areas and cause localised mould, damp and toxic spores very quickly. In the traditional building system this moisture laden air is released by the draughts caused by room vents.
An air tightness test is necessary, its not just to measure how much air is leaving the building envelope but also where its leaving. It is very important to identify these points and that the correct sealants, membranes and tapes are used. There is no point going around the house with a smoke pen and sealing the gaps with masking tape or silicone as it may perish and wont last long.

Feel free to correct me on any of the above or remove if you think I'm scaremongering

What would you use to seal the gaps then? What's wrong with silicone? I have used foil tape to seal the joints between the PU boards, I have also used silicone to seal the windows opes and the gaps that I could find at the edges of the ceilings. Any bigger gaps were filled with pieces of PU and expanding PU foam. I will be using the sticky expanding Pu foam that Im using to stick the composite boards to the external walls to join the board together as the plasterboard overlaps the insulation by a couple of mm which means the joints are far from airtight. I will also use this foam to seal the top and bottom of the composite boards to meet the flooring and ceiling. any other suggestions or comments on what I'm doing? Thanks!

ollie30

Google 'seda' For Info On Airtightness

marielle

ollie30 wrote: »

Google 'seda' For Info On Airtightness[/QUOT

Can you be a bit more precise? What does the SEDA you are referring to stand for?

ircoha

http://www.seda2.org/guides/index.htm is the link