ruggers

@nod Thanks I'll have a look at them, strange how they can offer better prices than the merchants when part of the main group. @CanskiJust had a look, no build base near and they don't deliver to my location. I will save the birtley name to try. It seems theres plenty of suppliers but lots of unheard of local ones and sometimes they offer better prices than the ones that come up on main searches online. My design is quite basic so I'm hoping it's all standard lintels, I've contacted catnic as you mentioned but theres quite a long waiting list at the moment so I'll have to wait. So using facing brick only, did you get away with the SD ones? They now offer a thermally broken lintel but the prices are off the scale for them.

Can anyone advise on where is best to buy catnic type lintels at a good price and the difference of where you'd use standard or heavy duty lintels. 150/100 have been specified for a 100 block, 150 cavity, 100 face brick outer. There doesn't seem to be as many places selling them as other items online. Last time i priced a load, builders merchants were expensive compared to online.

That price was for supply of gyvlon or cemfloor and their labour charge to set tripods to level the floor ready for them pouring.

If i'm working it our correct, your screed is £36m2 at 75mm, mine is £29m2 at 50mm. Divide 36 by 3 then x 2 (For 50mm) = £24m2 if i was using your prices. Wagons are often 4,6,8 m3 so you will be a full load at 8m3, I will be 3/4 of a 6m3

Thats around £5 per m2 cheaper than what I've been quoted at £29 m2. It's probably a combination of distance from the cement supplier to my site being further away as a local ones stopped providing it, and possibly reduced load compared to you, 8m3 vs my 4.5m3

Just jumping onto this post rather than start a new one. Is there much quality difference between Gyvlon liquid screen & Cemfloor? I was set for the Gyvlon but a local plant has stopped supplying it so it would have to come from mixer truck which might be too large for access. Prices last year for 50mm were going to be £21.50 per m2 for 83m2 (£1800) but a recent quote has increased this to £29m2 (£2400) which has increased the price by £600 for either screed.

Thanks John, I think what has confused me was standard air changes for a none MVHR house vs a house with MVHR. Although airtight, I wasn't sure if having MVHR increases or decreases ACH. I was thinking it increases the ACH because theres a fan controlling it which will always be more than natural ventilation? As mentioned before, wondering if the heat loss software, although we may change the ACH for a house with MVHR, can the software detect how much heat isn't being recovered at this higher rate or is it just detecting a higher heat loss due to more ACH. I've just found this (See attached) in an online manual for the software. So I've now selected MVHR at the default setting and all of the ACH figures per room have reduced, Is this suggesting I change the figure to 90 if the figure was 90% efficient? It seems a bit dramatic. Without MVHR heat loss is 6.1kw With default MVHR at 50 the heat loss is 4.5kw With setting changed to 90 the heat loss would be 3.24. MVHR doesn't save that much energy so I must be doing something wrong.

It was 20 inside and the recovered heat was 19. Can't remember what they said the outdoor temperature was at the time. I do think 90% efficiency isn't uncommon though. Do these figures mean your MVHR at 0.3 ACH is running at twice the capacity expected or half as good? I've not looked researched anything to do with ACH & how it's all calculated at this point only design, functions and performance.

I've spoke to the MVHR company today & they've confirmed with some cheaper units it's not always possible to know exactly whats being recovered, but with the likes of the Zehnder units with sensor monitoring, they have plenty of data to show some properties they've installed at having recovered heat at 1°C less than the indoor temperature at 20c. Is this data on a website for set areas anywhere or is it your own data? Interested for my own, I'm sure it's 9°C local. Interesting figures, good to see. Theres no doubt MVHR is of benefit, it's just making sure my calculations will reflect this. I'll check out the sheet Johnmo refers to as a comparison. In layman's, is this something we should consider as a factor or is it minimal and not so noticeable?

Storm dry seems an excellent product for this.

I will take a look at them John, always good to compare because sizing emitters can only be done once with UFH. I just imagined the sheet would require me doing a lot of long hand calculations with formulas which isn't my forte. Some experienced heat engineers I've been speaking to had said about using the heat eng. software as it was good, although they can do it via others means it would provide me with good results and use it themselves. I'm not sure if they have considered MVHR before though. My concern is how the software correlates with heat losses vs ach & heat recovery. I think I'm with Joe on this one to a degree (No pun intended). The chilled wind could act as a wicking effect at drawing the heat away from the dwelling, especially if wet mortar between face bricks, I may be wrong because the inner and outer skins are independent, but we do know that poorly fitted PIR in a cavity can have the same effect as a radiator in reverse. Air passes between the gaps from poor install and draws heat away from the inner cavity wall. Effectively no wind should be able to get in other than tiny weep hole vents but its possibly just from the difference of temperatures.

@joth This is my concern, that the software only detects a change of defaults resulting in more air exchanges per hour so it estimates that i require more heat than needed because it doesn't factor in the heat recovery percentage. I will look into this in more detail because a tutorial video i recall a mention of 50% default for MVHR but an option to increase the %. Is PHPP the passive house detailed calculation, do you have a passive house? I've included some attachments, the MVHR report is just one of the 3 companies who provided me with some details & a quote.

Of each room value? Why that figure? I'm hoping it will be answered at a later date once i pay for a detailed design with the MVHR company who can advise me what to add but MVHR won't know much about heat loss calculations or care so I need to make sure I can input the correct data to get my results accurate. As mentioned, a whole house of adding insulated plasterboard made very little difference but changing some parallel rooms lowest temperatures from 18°C to 20°C to match the 21°C design temperature shaved off 0.4kw total.

I think MVHR is a good idea, and I'm happy with the heat loss calculation although would like to improve it further. What I don't know how to do, is get the most accurate results from the heat loss software when installing MVHR as this could/will affect the air changes beyond their defaults. This can through the calculation out massively & I could end up under or over sizing my heat emitters which defeats the object. I'm aiming to get them as accurate as i can, so when fitted with weather comp the house is sized perfectly & feels good. Question is, what do i set the ach to in the software to reflect the MVHR install?

A good few replies from a late night post. I'll answer below. I believe MVHR to be good and having to have an air tightness test on new builds means MVHR or trickle vents, ones cheap, one isn't, but i hate trickle vents with a passion. So going down the MVHR route, I'm fitting a quality unit that can recover up to 94%. I have a good draft design that i will self install and have narrowed it down to two really good companies to complete the design, install & commission after speaking to a few of them. (Will select once overall quotes are in for all trades). So I've decided to make sure I apply a high level of air tightness & insulation detail myself after researching a lot on here & speaking to people. Heat engineer app followed by sending the report to the desk top version to fine tune everything. It will warm the incoming but would it not also be dumping some of the warm air outdoors continuously, 20°C extracted at 90% recovery would mean the supply air is 18°C? I sometime see quotes saying MVHR can lower your heating bills by 20%. In winter I probably wouldn't open my windows & never use trickle vents so it would be less than MVHR. I'd crack them open on catch in bedrooms for an hour or so in the morning or when cooking. It's probably not correct what i done, i was just trying it based on the attached screen shot, the heat loss software defaults all ACH to 0.5, 1.5 or 2 for various room types. Bad choice of words from me sorry, shouldn't have said standard. My calculations are now completed & showing as whole house loss of 6.11Kw based on all of my materials to be used with correct U-Values. This is 10% more than it would be because I've ticked the exposed area option being 125m elevated, 2 miles from the West coast in a windy area. What I'm surprised at, is by changing my 0.17W/m2K cavity wall insulation to a different U-Value to simulate how adding some internal insulated plasterboard at different thicknesses would improve things, it made hardly any difference at all and they cost 3x more than a standard plasterboard. Adding 37.5mm to the inner skin gives a value of 0.14W/m2K, adding 52.5mm gives a value of 0.13W/m2K. My 6.11Kw house heat loss only improves to 5.97kw and 5.92. It seems a waste of money adding the insulated board to the inner walls unless I've done something wrong?

I've been using some heat loss calculation software that many heat engineers use & I've accurately included all of my data & exact U-values. I've tried altering certain room temperatures from 21°C to 19C to see how it affects things room by room and the total. The software defaults the ACH per hour but I don't see any option to include the MVHR unit I'm choosing to use & include its efficiency. Zehnder Q350. Looking at an MMVHR estimate I received, it states some nominal air changes 1/h. I input one of them to a small second bathroom, overriding the default and i had to increase the ACH from 2 to 3.47 if this is correct? to see how it would affect the heat loss. It increased it much more than expected, so I'm now wondering how much this is going to negatively affect my overall loss. The standard heat loss for 235m2 is 6.4kw with 10% extra added on due to exposed area setting. How should MVHR be included into the ACH section once I have a detailed design? We know with UFH/radiators and weather compensation that its very important to get accurate heat losses to size the emitters. I was also hoping for a good heat loss result.

Thanks, I might give them a call tomorrow. If 150mm can get down to 0.11/0.12, it's possible that the 100mm slab under the insulation adds a small amount of value to the 150mm insulation and brigs it to 0.10W/m2K. Eco therm and quinn therm were always cheaper than kingspan.

Thanks JohnMo I have a ground floor SAP target of 0.10 W/m2K and the plans state, from the ground up. 1. Min 150mm sub base 2. 50mm sand blinding 3. DPM 4. 100 Concrete slab 5. 150mm PIR insulation 6. 50mm Liquid screed (With UFH pipes embedded) Someone said that I'd require 170mm of PIR to achieve 0.10 for the floor so I wanted to check if 150 was going to do it or not.

An after thought question on this.... If W/mK is for a thickness of 1m, is W/m2K always based on 100mm?

Thanks @SteamyTea I wasn't sure whats a figure worth caring about and what's insignificant and just looks better on paper. 0.17 vs 0.18 vs 0.19 @Temp I missed the surface effect from the calculation both sides and see you have reduced the dab gap to 10mm from 15. Boffin of the night award for you tonight 🏆. I'll keep my dunce hat on, brains cooked for the night. Hopefully now I have enough figures to input everything as rockwool provided the partition walls, loft and intermediate floors values. I did look at the examples again & used the formula you provided and now understand how close it makes it. Thanks again both of you.

I still thought it would affect the end result because the insulite R layer says 0.204 and the dense is 0.085 so once totalled and then divided the answer couldn't be the same considering as a bare block one is twice as good as the other. Is my example ok to use? 12.5mm plasterboard R 0.060 + 15mm air gap R 0.170 + dense block R 0.085 + 15mm air gap R 0.170 + 12.5mm plasterboard R 0.060 = 0.545 Then U = 1/0.545 = 1.84W/m2K

If i'm applying your methods correctly, looking at these two further examples attached & using the R values they've used, I'm getting 1.84W/m2K for plasterboard - air gap - dense block - air gap - plasterboard. And for the insulite it's 1.5W/m2K? I'm still baffled how both blocks equate to the same U value when combined with other materials.

Thanks Temp for clearing this up. So to obtain U, I require the R value of the material? So on it's own, the insulite is is twice as good at preventing heat transfer compared to the dense? I'm not sure if this is of benefit for internal walls or not, I'm only losing heat to another room but the insulites sandwiching 100mm PIR are 0.01W/m2k better between my house and attached unheated garage if thats worth bothering about. Insulite are around 20p per block more expensive. I was going to use them for my inner leaf of the cavity wall until i found out they are just the same as dense when combined with the PIR.

Can anyone help me with obtaining some material U values to input into the heat engineer software I've been using. I'm not smart enough to complete the calculations required when looking at the formulas 😚. I have attached two data sheets for the blocks I'm going to use. One for a dense block and one for an insulite block. Dense is showing as 1.17W/m2K and the insulite is 0.49W/m2K. I would like to know what the U value would be for each type of block if used on their own for internal ground floor load bearing partition walls with a 12.5mm plasterboard (0.210W/m2K) dabbed onto each side. Am I correct in thinking that as a bare block with no plasterboard, the U value for internal use would just be as per data sheet being 1.17 and 0.49? For a little info. for anyone else - A member of the brick company provided me with some personalised data & an explanation for each when used in a cavity wall situation with PIR and strangely they both equal the same U-value. With both blocks used in the below layout, a U-value of 0.17W/m2K was obtained. 12.5mm plasterboard (0.210W/m2K) - 15mm dab cavity - 100mm block - 100mm PIR (0.22W/m2K) - 50mm air gap - 100mm concrete brick - Total = 383mm Without the cavity air gap having the PIR sandwiched between the blocks made the insulite at 0.18W/m2K and using the dense block was 0.19W/m2K. DENSE Datasheet - WEB July 17.pdf INSULITE Datasheet - WEB July 17 2.pdf