Improving insulation in house with many wall types!

[Will]

We've just moved in to an old bungalow. It was built around 1920 and has a variety of different types of walls. 

 

The original construction appears consist of two timber framed walls (basically external stud walls, the framing seems to be 4x2), and two solid walls.

 

Later, two extensions were added. One appears to be cavity wall, and one seems to be single skin blocks. 

 

The timber framed walls make up probably 40% or so of the total length of the external walls, with the original solid walls a bit less than that. 

 

We really want to achieve a high level of energy efficiency when we do the place up. Ideally we'd get it up to a standard where we could install MHRV - no idea how realistic this is but we had it before in a flat and loved the fresh air. 

 

So my question is, what happens if different walls have different levels of insulation? I think that insulating the timber framed walls will be fairly straightforward, but I don't know if we'll be able to stump up the cash to pay for external wall insulation for the solid walls.

 

If we insulate most walls, but leave some uninsulated, are we creating a recipe for condensation on those colder walls? Or any other reason why it is a bad idea? 

 

We are planning to insulate under the floor and the loft too (obviously). 

 

Does anyone have any thoughts? 

[Dreadnaught]

If you're a fan of avoiding the performance gap (between and building's re-design and its actual performance), have you heard of the EnerPhit standard? It is Passive House but for retrofit.

 

More info here: http://www.passivhaus.org.uk/page.jsp?id=20 if you're interested.

Edited April 6, 2018 by Dreadnaught

[Will]

Thanks for that! That's helpful, I'll have a read.