SimonD

Not without damage as the felt is properly fixed. I have to say that compared the the old bungalow, this garage was well built with attention to detail.

It's just like this but with ties every other rafter.

I need to create a loft in the existing garage before I build the new one. It's got a traditional pitched roof with rafter tiers every other rafter. The ties aren't of sufficient size to use as rafters across the current span, so I'm considering how to easily add joists across to create my new loft space. Options I'm considering are: 1. Cut ends of new joist on the diagonal and then fix to existing wall plate - but with sufficient bearing on the wall plates I don't know if I can slot them in; 2. Install wall plates to the wall just below the ties and fix new joists to these (garage has sufficient height for this); 3. Sister the ties with the new deeper joists - and add new ones to rafters without existing ties. Walls are ashlar faced breeze block. Any thoughts, ideas and experience to help me decide? Any details I need to be aware of?

I have to say, John, that I try to avoid WB boilers like the plague. I think their designs are awful, I hate working on them and I would definitely never install one (although I have installed one, once!). I think the 8000s are worse than ever, but lots of installers seem to like them for whatever reason. I've never been called to investigate this specific problem, only that radiators aren't getting hot and this is almost always to do with a system balance issue and not the boiler itself. When I do system diagnostics involving temperature measurement I always ignore the internal boiler temperature given by the sensors and instead use my own clamps to as close to the boiler as possible. This is because I very often find discrepancies between displayed flow/return temps from internal sensors and those measured immediately outside the boiler, it's not just with Worcester. The only times I take the internal sensor readings more seriously, is if I see the boiler cycling when my readings suggest it shouldn't and 5C difference is just not unusual in these circumstances. This is why my approach here would be to ignore the boiler and investigate how the wider system behaves over time. A recent example is a hall where I installed a boiler a few years back. I designed a low temp system and explained all this to the caretaker and for several years the system ran beautifully. This year I received calls to say the heating wasn't working and the hall wasn't getting warm. I went and looked at the boiler and found out that the new caretaker was expecting the system to heat the hall up from freezing cold to between 18-20C within 40minutes so they'd even cranked up the boiler output to 75C! I explained to them that they should drop the flow temp back down and be a bit more patient as their bills had dropped noticeably since I installed the system. So in short, sometimes it's about education!

I have to jump in an ask why would a system with the installed pipework as described ever need an secondary pump of 8meters head, let alone a LLH. I find it almost inconceivable that the index circuit on this system needs an extra few meters of head above the 4 it's already got, unless the installer had accidentally welded shut the pipes somewhere. I've worked on Worcester 8000 system boilers that are fine under more demanding system conditions. I would suggest doing a factory reset of the boiler (maybe that was done when the engineer came?) to get everything back to default. Then run the system taking regular temperature measurements through the system. Pinpointing which rads are problematic and then taking a methodical approach to understand the whole system behaviour. But I'm also wondering what exactly is the problem you're attempting to fix? If it's this: Then we need more specific information about what exactly you define as quick and from what beginning state to what desired state.

The basis for my calculations came from the Handbook of Domestic Ventilation by Rodger Edwards. It's a book that's getting a bit long in the tooth and could really do with another edition, but the fundamentals, including various formulas are there. Its section on PSV is very comprehensive and shows that it works, and if facts works better in air-tight houses because they have more control - e.g. studies in Denmark show a mean ACH of about 0.45 with PSV with no detrimental effect on air quality. In terms of understanding implications of hygroscopic materials, I did a lot of research looking at studies across Europe and North American to gain an understanding of how these materials reduce ventilation rates due to buffering moisture load - so, for example in cases of PSV, with a house that does not have moisture buffering peak RH can reach 75% for short periods (but not periods long enough to cause issues with condensation etc, in the building) and with moisture buffering, this can easily be reduced to peak loads of 60-65% during peak moisture load, like showers, baths and cooking etc. However, the area is still pretty poorly research tbh, so there is some guesswork required and a careful attention to detail. I have made sure I choose materials through the whole of the fabric, including paints - so everything is finished with clay paint. I also use gypsum plaster as opposed to lime because gypsum is both vapour permeable and hygroscopic whereas lime is only vapour permeable - which is why lime can survive damp stone properties and gypsum can't, but gypsum is excellent in a newly built of deep retrofit property (but it's also been used in Italy for a good couple of thousand years because of its moisture buffering properties). We also have clay bricks on the ground floor, which are brilliant for moisture buffering. Yes, it's bouyancy and also wind - if the PSV is designed and installed properly it should benefit from a negative pressure zone above the roof. It's actually been shown that if ventilation at the bottom of the stack is increased, the flow through the PSV increases, which is one reason why PSV performs better in airtight buildings that have controllable ventilators - in leaky houses you can easily get over-ventilation with PSV.

You've also got the option of just buying a second hand unit too, which you don't usually get with a gas boiler. Or at least I wouldn't install a second gas boiler for any of my customers.

Not really. Theoretically it should be easier than swapping out a gas boiler. Even connecting the flushing equipment is easier as you can do it off the isolators outside.

I bet you were 😊

MCS and the consumer protection companies don't really like this structure any more. They prefer the BUS grant to be subtracted from the quote.

The installer will make an application for the grant to confirm eligibility as soon as you sign on the dotted line for a contract. It's normal practise to ask for stage payments first and then apply for the grant after commissioning. Once the initial grant eligibility has been confirmed with OFGEM the installer has 120days to finish and apply for grant redemption.

There always lots of content about why not to get a heat pump installed, but I would like to know why you chose to get a heat pump installed instead of a fossil fuel boiler? Doesn't matter whether it's for retrofit/renovation or new build, I'm just interested to know. And what were the pain points that were most difficult to overcome? Was it just the price or is it in line with so many posts on BH that it's difficult to find a decent system designer and installer?

We are 4 plus dog in a volume of above 900m3. But as I mentioned above, ventilation requirements change dramatically once a hydrophilic fabric is introduced into the equation. So, to quote from an earlier study I read when deciding on my design: https://web.ornl.gov/sci/buildings/conf-archive/2004 B9 papers/002_Simonson.pdf Now, it does acknowledge that consideration regarding air polutants is probably separate, but other studies using MVHR show similar reductions on ventilation requirements simply because moisture drive such a significant proportion of those ventilation requirements. Yes, indeed. At some point when I actually find some spare time, I might draw together my collection of research into this and building physics just so there more readily available reference.

SS is used for traditional metal standing seam roof clips and screws.

There are some articles out there that talk about this. If using over-lay, then it must be one that uses an insulated backing such as pir. In effect, this creates a decoupling with the slab and as it increases thermal resistance to the slab, it pushes it upwards instead. However, you need this to be properly calculated by someone who knows what they're doing because floor down losses also depend on the shape of the floor and external sides.. It's probably going to be better than over-lay on a suspended floor, but neither are that ideal into uninsulated floor. The other thing you need to consider is that you'll be raising the finished floor height and this will have an impact across your entire house and will also impact your stairs, which may need modification to still comply with building regs.