Old farmhouse renovation - baffled how to heat and ventilate it

mulletamoeba

We are in the process of planning to restore an old derelict farm building and converting it into a residence. The walls are solid, a mixture of brick and stone. Roof will be stripped back and repaired. Internal upstairs floor will be lowered. It will basically be gutted and started afresh.

On top of an internal lime plaster, we plan to insulate with a mixture of blown cellulose and also some wood fibre boards in places. We are also aiming to make it airtight. It will be impossible to eliminate all thermal bridges completely due to the nature of the building. The windows will be casement style. We will have three solid fuel stoves in the house which will be around 35000sq ft.

There are a baffling array of options out there for both heating and ventilating and it's very difficult to make a decision. The bulk of the energy related spend will be on insulation and air tightness so we want a heating system that is reliable and affordable and will be appropriate for underfloor heating. Also we want one that can be readily serviced in the west of Ireland.

Regarding ventilation, is an appropriately specked MVHR system something worth investing in or is the expense (in the region of 10k before running and servicing costs I've been told) something that is pretty hard to justify. Perhaps a more simple and cheaper ventilation system would be the way to go.

Lastly, I was told that Despite being widely used for that purpose that OSB is not a reliably airtight product and that using an intello membrane or similar would be a better choice. Is that the case?

It's going to be a bit of a money pit but any relevant experience or views would be welcome!

Hootanany

popcorn opened:D

mulletamoeba

Giant coke and some white mice to go with that??

4Sticks

Why don't you start on the outside i.e use external wall insulation ?

mulletamoeba

Thanks for suggestion. It is a protected structure. Although it would be simpler, The external finish and in particular limestone door and window surrounds would be compromised by external insulation.

DOCARCH

mulletamoeba wrote: »

It is a protected structure.

Never mind external insulation, you will possibly need planning permission to do what you are thinking of doing internally...have you got planning permission and/or sought a Section 57 Declaration from the Local Authority?

mulletamoeba

Yes, planning permission is in place

4Sticks

I shall take it that you are aware that a protected structure cannot be gutted as you describe without detailed planning permission and for the purposes of this thread assume you have all that consent in place.
Assuming also that you are not extending by more than 40m2 you are not subject to the new building control regulations your works will still be subject to the requirements of the technical guidance documents of the building regulations. For a materiel alteration you need only insulate your external walls to 0.35 w/m2K to comply with Part L and in order to avoid trapped moisture damage when dry lining it would be sensible to leave it a that.

mulletamoeba

Thanks.

All planning permission in place.

Aware of need for vapour permeable insulation and lime plaster and paint to avoid condensation etc on solid walls.

Buildings such as this are exempt from Part L and we have been granted this.

I guess my question relates to whether anyone has experience of older buildings and using modern airtightness technology in them.

We have a conservation architect and engineer on board, as well as a competent builder and an airtightness installer. They are looking into these issues and reckon it can be done. For what cost is the question. I'm not making the decisions based purely on boards.ie! Just looking for anyone else's personal experiences or tips.

4Sticks

Back to your thread title.

You approach heating like you would any other building really - calculate the heat load and take it form there. But taking a stab at it I suppose that a reasonable amount of energy saving measures ( u vlaue and air tightness measures ) would take you to about a 50w/m2 load. So 50 x 3500 = 17.5 Kw heat load. Add say 5k for DHW and then + 20 % for storage and distribution losses you get ( 17.5 + 5 ) 1.2 = 27kw boiler.

It looks like you will be dry lining your walls so low thermal mass will respond best to a quick response heating system so conventional lphw system with rads and high efficiency oil boiler . No mystery.

4Sticks

If you are gutting the place it would a real missed opportunity if you dont instal mvhr. With expert help and an exposed structure you can plan the concealad duct runs.

Then air tightness. Dont let let excellent be the enemy of very good. If you aim for a q50 of 5 or 4 that would be good result. No need to get ratholed chasing a passive level of performance.Definatly carry out the AT test to know where you are at in any event.