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Windows and Tenders




I'm currently awaiting the Architects tender documents for review. It's been a two month process and I've been making inquiries into specific heating, MVHR and window options. Budget as always is a worry. I've drawn up a list of timber frame companies and builders and met those on the short list face to face. The Architect will have other names to drop I'm sure but getting a feel of the building pulse and talking with the builders really helped me identify the risks as they see it. Masonry vs Cement Board was a concern, Architect said masonry is 1/2 the cost, builders has it's about the same. Shows what they know! 

I have a few quotes for MVHR and for all these options, getting a Passive House Certified unit was recommended. BPC are my lead choice (Ventaxia), Zendher and Paul while better are proving too expensive. 

Heating will most likely be ASHP for now. There's too much pushback to get a SunAmp in up front. I'll get the house built and review. Nick gave a great idea about a willis heater but the Architect is opposed. Well, we'll see what the tender responses look like and how this plays out. They tell me I can choose a cheaper ASHP later but later may be too late. 


Windows have been the most frustrating area. I've been speaking to over a dozen suppliers. Most don't quote the specs I'm after, don't have the glazing options I need or have never heard of the performance certificates the Architect wants. Despite quoting what I need, you usually only get a standard response. Sure, they're nearly passive you'll be fine..!! The PH database doesn't tell you which windows are available in your local area. It's been hit and miss contacting them directly. Some supply to Ireland, some don't. 

Previously I'd thought Rationel would be an easy win but the G values are fixed and I need higher ones for my house. I'm hoping for top hung, outward opening alu-clad. The Architect gave the following guidance for the specification they require:


Glass Technical Information

•         Ug according to ISO EN 673

•         G Value according to ISO EN 410

•         Psi Glass Edge according to ISO EN 10077-2

Window Frame Technical Information

•         Uf  according to ISO EN 10077-2

•         Psi Install according to ISO EN 10211

•         Widths of Frames for Top, Bottom and Sides


Then this follow up:

“The ideal window would be the one with a low Uf value around 0.8 w/m2k, with a low spacer thermal bridge around 0.02 to 0.03 w/mk, thin frames. The glass is also very important component and ideally the g value is as high as 65% to 67% and the Ug value as low as 0.5 w/m2k.”


I'm getting good at taking a quote and pulling out the Uw and other values into a spreadsheet for analysis. Most only give the Uw however, not Uf, g, PSI glass edge etc that's needed. I've two good window quotes in but while Rationel were €14K, these two are €28K and a third €40K! I've prices @ €20K from a few but either their performance doesn't match or they can't provide sufficient information. Velfac come in at €14K but just as I was about to breathe a sigh of relief, I visited their showroom and let's just say I won't be buying if I can help it....

One piece of advice, send the spec, get the price and ALL the performance details and independent certificates to prove it and only THEN bother to visit a showroom. If you're at a tradeshow, fine, otherwise stick to email and phonecalls! Some sales people are very pushy about a face to face. 


I've two more windows people who are getting back to me. At least I've found windows that will do the job. I hope to list one of them in the tender. The lift and slide may end up being Internorm and so may the door so I might still mix and match but we'll see. There's more to consider of course, Guarantee, supply vs fitting and VAT, is the agent solvent etc


At least the Velux windows were easy although over €1K a pop!! 


Hope to have prices / quotes back in November for a build in 2019. Brexit takes center stage of course. Should I delay selling or building, I'll have to wait and see. 


Window Model / Supplier list: 



True Windows

Nordan Ntech





Zyle Fenster


Tercoco Velfac

Thermax 2 Ultra

Oknoplast Winergetic (PVC)


Munster Joinery









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Interesting that Rationel were one of the best and the cheapest, that was my finding. In fact the only ones that quoted me better Uw values than Rationel, were Internorm, but at twice the price.


Before you get too bogged down in you "must" have a certain Uw or Ug value, do a heat loss calculation. Compare how much extra heat will be lost through what Rationel are offering, compared to the best you can find, then work out the extra heating cost of that extra heat loss and work out the pay back times.  I think you may find you will never recoup the extra you have to spend to get better windows.


I am certainly pleased with the look and quality of my Rationel Aura plus triple glazed aluminium clad doors and windows and it does seem strange to hear talk of rejecting them because they are not good enough.


If you want to try a couple more, add Katzbeck and Russel Timbertech to your list.

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Interesting, also, that MBC appear to be quoting on the windows.  This wasn't an option when I signed with them.  Do you know who they are using as their supplier?

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What’s the concern with Velfac? We’ve got them fitted. Decent kit in my view. I would agree they are a bit of a bind to deal with though. Let me know if there’s owt we can do to set your mind at rest or qualify your concerns 

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MBC Project is a separate company to MBC Timberframe. Will have a look at those other two ProDave. Maybe Velfac isn't as bad as I think but I'll definately keep them in mind for my budget. Thanks all! 

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