Mechanical ventilation behind insulation

[Blame]

I'm sure this has ether been done to death, or there is a good reason why it can't be done at all. Problem is I can't find anything on the net. 

 

Anyway, I have been search for a cheap northern England property. No plan to buy for at least a year, but I figure on learning the pitfalls now. So what I have discovered is a lot of cold soggy houses going cheap. By the looks most with solid walls and ground floors far too close to the ground.

 

So, Suppose I bought a big one, covered the inside walls with battens in a maze pattern, mounted insulated plasterboard on the batons and forced air through the maze to keep the walls dry?

 

Not that I would buy one openly covered in mould but I can imagine all sorts of temporary fixes that won't show themselves till the ink is dry on the contract. I can also worry about insulation blocking drying to the inside (especially as the outside is likely sealed with paint).  

 

I'm more thinking that if I'm mounting insulation it ain't going to cost more to arrange the battens as a maze just in case. For that matter how expensive can a few fans be?

[Ian]

@Blame

If a house is damp there's usually an obvious cause and I'd be looking to identify & sort out those problems first.

 

Usual causes of damp include:

• defects in roof or with gutters/downpipes. 
• If the external walls are solid brickwork (IE no cavities) check condition of pointing.
• rising damp - do the walls have a dpc?
• check ground levels relative to FFL in the house.
• often older houses can have problems with condensation due to the way they are used (or rather abused) - these issues can be solved.

 

[Jeremy Harris]

Welcome.

 

The result would be a few problems.  First off, pumping air behind the insulation may well result in the damp on the walls getting worse, rather than better,  If the walls are cool, as they will be when you add internal wall insulation, then moisture in any ventilation air is more likely to condense on them.  The effect of the insulation would be reduced, too, as cold air would be flowing behind it.

 

Probably the best way to improve an older solid wall property is to fit external wall insulation, so the old walls are now inside the heated envelope.

 

@Ian has already mentioned the usual reasons for damp, and my experience of renovating old stone cottages has been that 99% of damp problems can be resolved by fixing places where damp is penetrating (leaking pipes and gutters, high ground outside, etc).  The very best fix for so-called "rising damp" is just to lower the effective ground level around the outside of the house, perhaps using a French drain and dimple membrane to ensure that the water level outside is always well below floor level.

[Blame]

Ian. Well yes. Does that mean that a terraced Victorian house with a ground floor practically flush to the pavement won't have any otherwise soluble problems?

[Ian]

2 minutes ago, Blame said:

Ian. Well yes. Does that mean that a terraced Victorian house with a ground floor practically flush to the pavement won't have any otherwise soluble problems?

Usually Victorian era houses have suspended timber construction to the ground floors. The original design would have included a ventilated floor void under the timber floor with air bricks on the outside of the house (front & back) and it's very important that this ventilation path isn't blocked when external pavement levels are altered. If the ventilation is blocked it can lead to problems with dry rot in the timber floor.

[Blame]

JSHarris. Thanks for the welcome. Stone would be nice but what I am seeing is brick. I did figure on the cooling air condensation problem. Can that be solved by sensors and controls so that its only on when condensation won't happen and ether nobody is in the house or when cooling isn't a bad hing?

[Blame]

Ian I am usually seeing air bricks but from the photos they often look above the level of the floor. Single thin doorstep to street. My gut reaction is just avoid... but sometimes its an awful lot of internal space for the price.

Edited June 22, 2018 by Blame

[Ian]

3 minutes ago, Blame said:

Ian I am usually seeing air bricks but from the photos they often look above the level of the floor. Single thin doorstop to street. My gut reaction is just avoid... but sometimes its an awful lot of internal space for the price.

There's usually a trapdoor or access panel in the floor to allow you to get down under the floor and inspect the void. Often they can be found in the floor of the cupboard under the stairs.

The other thing to look out for in houses like that is later extensions to the rear of the building which may have blocked off the air bricks at the back of the house and therefore preventing cross-ventilation of the sub-floor void.

[Onoff]

Quite common too to see slate or pitch damp courses bridged by later render. 

[Blame]

Ian -- Trapdoor - wow now that's a useful bit of info. Thanks. I'm Looking at Barrow in Furness. For now, only over the net. Difficult to spot anything that hasn't being repetitively extended. Counted 6 on one property like some sea creature repetitively outgrowing its shell. The council there has great Aerial maps. On the whole I think extensions reduce the value. But then I figure the 12 foot wide 2 up n 2 down are not salvageable as family homes. 

[Blame]

Onoff  -  good to know. Must say I ain't spotting a lot of evidence of damp courses in the photos. That might be why. But could they be mounted on engineering bricks instead?

[Blame]

This is the sort of thing I am looking at.

 

https://www.rightmove.co.uk/property-for-sale/property-54945384.html

 

Worth over £ 100,000 in good nick but would it eat £60,000 and still be hungry?

[Jeremy Harris]

1 hour ago, Blame said:

JSHarris. Thanks for the welcome. Stone would be nice but what I am seeing is brick. I did figure on the cooling air condensation problem. Can that be solved by sensors and controls so that its only on when condensation won't happen and ether nobody is in the house or when cooling isn't a bad hing?

 

Go for the simple solution every time, ideally one that's been proven.  Lots of buildings have been fitted with EWI now and it's probably one of the better ways of upgrading an older solid wall house without increasing risk to the structure.

 

Your example in Barrow is a good candidate for EWI IMHO.  The only issue to overcome is the eaves overhang, but you only have the front and rear walls to do.  The aesthetics of stepping out the front and rear wall by 100 to 150mm needs looking at, but overall I'd say EWI would be a good option.  It also leaves you with all the warm internal structure as is, so minimal disruption to existing fittings. In terms of added value it's had to say, as Barrow is a low price area, and so this will restrain any uplift, but if you're not looking to make a quick profit, but enjoy a comfortable house with lower energy bills they go for it.  There will be help forthcoming from here for sure, as I don't think we've seen a major EWI job documented her before.,

[Blame]

JSHarris - Um Newbie here. What is EWI?

[Jeremy Harris]

1 minute ago, Blame said:

JSHarris - Um Newbie here. What is EWI?

 

 

External Wall Insulation.  It's a system of bonding and fastening insulation to the outside of a building and then giving it a smart rendered finish.  It can be a DIY job (with the possible exception of the new render) and effectively wraps an insulated tea cosy around the old house.  If the old walls can't get cold then they won't get damp, so it kills two birds with one stone.

[Blame]

Good solution - but not sure I would get permission for a street house. That pebbled paint is everywhere but not spotted others with insulation poking into the public sidewalk.

 It would be for my daughter who has eye problems and thus will never drive. Everything has to be an easy walk away and that probably means town house flush to the street. 

[Jeremy Harris]

9 minutes ago, Blame said:

Good solution - but not sure I would get permission for a street house. That pebbled paint is everywhere but not spotted others with insulation poking into the public sidewalk.

 It would be for my daughter who has eye problems and thus will never drive. Everything has to be an easy walk away and that probably means town house flush to the street. 

 

I doubt you'd get problems with permission, and you may well get a grant to help with the work.  Worth looking at, as it can be a very good and cost effective solution.

[Blame]

Cool. Still nice to have alternatives in case the permission falls through - you don't get a lot of time to ask with auctioned property.

[ProDave]

Another vote for find and fix the fault causing the "rising damp"

 

I bought a 1930's semi that was very damp in one corner, made worse by the fact the owner had tried to hide it by lining that corner with polystyrene tiles and wallpapering over it.

 

The fault was just that the pebbledash was bridging the damp proof course, coupled with the ground being too high in that corner. Once that was fixed it dried out and I didn't even need to re plaster.

 

That didn't stop it being a cold and expensive to heat house. Knowing what I know about houses now, I would not be in a hurry to go back to one like that.

[Ferdinand]

13 hours ago, Blame said:

This is the sort of thing I am looking at.

 

https://www.rightmove.co.uk/property-for-sale/property-54945384.html

 

Worth over £ 100,000 in good nick but would it eat £60,000 and still be hungry?

 

IMO possibly, depending on the project.

 

To me, having had EWI quotes on about 5 different properties including one of detached, terrace, semi and 2 bungalows - though not a 3 storey terrace, that looks like 10-18k depending for EWI plus scaffold levy in your area, depending eg on prep required and the complexity of the back.

Whether 60k in total would do it depends on the auction price particualarly, but taxes and obvs sharks in the custard of the legal pack and what standard you renovate to,  if you are self-renovating, finish you want, and how good you are.

 

Council grant may be possible, and with 5 or 6 doubles potentially a good yield if a rental. At that price may have 'flats' potential.

 

Ferdinand

[Blame]

Ferdinand 

 

I have research the area and one thing I am sure about is breaking houses into flats is a mistake. The reverse would be good. 

 

That may be against conventional wisdom but flats are going for as little as £10,000. And for evidence:  https://www.rightmove.co.uk/property-for-sale/find.html?locationIdentifier=USERDEFINEDAREA^{"polylines"%3A"atoiIfrxRbGmkCpZc}Eh_%40kb%40zf%40mc%40xx%40}Ud`%40lBfI`\|e%40dPhq%40am%40hfAevBtdHjC}`En`GkxBd`Fi[tt%40oYbPqy%40vVi~CpVkjAi_%40"}&minBedrooms=6&maxPrice=120000&sortType=6

 

Its all about the history. The railway and shipyards created a huge building frenzy in the late 19th century with the inevitable result. The town is full of decaying narrow 2 up and 2 down terraces built to a budget. Most have since been extended with bathrooms and rabbit hutch kitchens but they simply don't make good family homes. Then came the demise of the British ship building industry and the population fell. Right now those properties have the value of their renovations and that is it. Difficult to rent them whole and in good order for £90pcm. You can imagine how picky renters can be for flats.

 

There is still work for some building nuclear submarines but that is well paid skilled work. My guess is most of them commute in by car from the new suburbs.  If my daughter gets her provisional offer of a job there then she would too - only she will never drive and the bus services are minimal.

 

The town's future appears based on the Government's belief that atomic bombs make a better world - and that us citizens are happy to pay for the delivery by submarine. Not convinced myself but the council's apparent plan to slowly bulldoze the lot and replace with car parks sort of appeals. 

 

So my take on the property would if anything be to drop it down to the original 4 bedrooms, and think of it as good for perhaps 3 sharing with the lure of loads of personal space. The single bathroom being the limiting factor. I also see not a lot of profit in maximising internal space so lots of thick budget internal insulation is my thought.  

[ProDave]

I have only been to Barrow once, out of curiosity.  It lives in my memory like Merthyr Tydfil as a place that begs the question, why would anyone live there? (sorry to all residents of those places )  Run down does not begin to describe it.

 

I am not convinced bargain basement properties have much potential to make money. Polishing a t**d springs to mind.

[Jeremy Harris]

2 hours ago, ProDave said:

I have only been to Barrow once, out of curiosity.  It lives in my memory like Merthyr Tydfil as a place that begs the question, why would anyone live there? (sorry to all residents of those places )  Run down does not begin to describe it.

 

I am not convinced bargain basement properties have much potential to make money. Polishing a t**d springs to mind.

 

Same here.  I had to go and stay there for a week whilst doing some work at the base, and it struck me (no offence intended) as being at the arse end of nowhere.  Everyone I was working with at the base said the same, and pointed out that they all lived out of town.  You only need to drive a few miles out of Barrow to be in some really nice areas.  Not really sure why Barrow itself is so run down, especially as the pay for those working at the base is probably higher than average.

[Blame]

JSHarris, ProDave

 

Well sometimes life doesn't go quite to plan. My daughter was about 3 months to finishing her Masters in engineering but she was getting headaches, so she went an opticians. It went rather downhill from there but maybe she will finish it now just a year late. She even got to keep half her sight and though most of her hair fell out its beginning to grow back.

 

Half blind engineers can be a bit of a drag on the market too so its all about what she can get. Anyway, as I pointed out, she ain't going to be driving and the local busses are a bit limiting . Hence the need to look at town properties such as they are. 

 

Must say there are a very few more modern properties within a brisk if cold and wet walk. In the end that will probably be the vote but I aim to cover all options.

 

Anyway to answer the question "Why would anyone live there" it would be because it's ether that and a toe hold into a well paying career or quite likely the doll.

[Blame]

Final Thoughts:

 

First nobody had much to say on active ventilation of cavities. And what was said was not encouraging. Given that if it was viable somebody would be doing it, I will take that as a strong No No.

 

Second I must thank Ian for mentioning suspended timber construction to the ground floors. I had not thought about the costs of replacing all that potentially rotted wood, or the practicality of checking in advance for an auctioned property. That in itself means I will not bid on a properly that lacks a visible ventilation path under the building and above street level. The example showed a property with only one ventilation brick and that level to the street. It is as likely to be an entrance for water.   

 

Finally I think you all should worry a bit about the "property developer" mindset. Maximise the number of bedrooms & bathrooms, optimise the use of every square inch. Usually a profitable approach but it is based on the assumption that people will take cramped living and pay well for it because they can't afford more. A more general philosophy is that people will pay what they can afford - and if they can afford more, they will. So when housing is cheap more must be offered. Something must stand out - space, location, insulation, underfloor heating, whatever. 

 

As example of this mindset take ProDave's comment: "Polishing a t**d springs to mind". It just shows a lack of imagination. The area might lack elegance but it is close to good schools,  supermarkets and well paid work. If that is matched to a property offering lots of easily heated internal space per inhabitant then you have something in demand and of limited supply. Check out the local availability of properties with 3-5 good sized bedrooms that haven't been extended beyond all good sense. I have. Rare and sold fast.