House building u values

ginetta

I am planning to have a house built using the turn key method. Various companies I have approached quote certain u values for walls, roofs etc., and I am wondering if there is any measurement, like the blower door test for airtightness, that would confirm after building that these have been met.

AJL

Hi Ginetta,

the blower door test will only tell you how air tight the house is. It is not going to tell u theheating requirements. See attached info on U values.
they need to be telling you what are the heating requirements for the house going to be. These are normally presented in KwH with a passive house at 3 kwH. They should be able to give you this info as they are supplying all materials for the build. they plug in the U values and the air tightness of the house to come up with a kWH value.

Mellor

AJL wrote:

Hi Ginetta,

These are normally presented in KwH with a passive house at 3 kwH. They are represented in KWh/m2y. It makes a difference to what the value is. And a passive is isn't 3KWh/m2y, that value is very low and levels higher than that than that also could be classed as passive
They should be able to give you this info as they are supplying all materials for the build. they plug in the U values and the air tightness of the house to come up with a kWH value.also the energy usage rating of a house, KWh/m2y, is dependant on alot more than the material u-values and the airtightness.

What values did they quote you for the various elements of the house??

AJL

Hi Mellor

. i was giving my understanding as a lay person building a self build house for the first time and was passing on what knowledge I know. I will refrain from replying and will yield to your superior knowledge.

Mellor

AJL wrote:

Hi Mellor

. i was giving my understanding as a lay person building a self build house for the first time and was passing on what knowledge I know. I will refrain from replying and will yield to your superior knowledge.

I wasn't trying to offend you, just expanding on the original point. sorry if i came accross that way. I only wanted to complete the info for a layperson so that they wouldn't be confused by the jargon the companys throw out.

Do-more

I think the point has been missed as to what Ginetta is really looking for, the pertinant question is:

ginetta wrote:

I am wondering if there is any measurement, that would confirm after building that these have been met.

I'm not sure of this so perhaps someone can expand, but I think that an Energy auditor using a thermal imaging camera will be able to measure heat loss from your building, whether they will be able to determine U-values for individual components I'm not sure. But I would imagine that they will be able to easily pick out weak spots in the construction.

AJL

My friend had a thermal imaging camera from work. He put it on my old house and you could see around doors and windows where the heat was escaping. i am not an expert but this would tell you where to seal up. If you are looking at a turn key house and they are going to make it airtight a blower door test will let you know where air is getting in so you can block these up.
As for the U values Ithink you have to check out the reputation of the company. If they have a good rep and they say U values are **** then you have ot take them at their word . Don't know if you can measure the U values afterwards.
If they tell you what your heat requirements will be, the u values of the materials such as windows (to see that they are to your required spec) and maybe they will do a blower door test
. Would suggest you might look at a ventilation system and not the grills in the walls where you cannot control air infiltration.
I am in the middle of building a Kingspan Tek house. Ventilation company had to know the U values of all materials used plus the air tightness of the house (theroetical from kingspan). The then worked out my heating load which is 9 kwh/m2y (is that right mellor!!). i wil lget a blower door test done to ensure I have an airtight seal on the house. Hope this is of some help.

Viking House

ginetta wrote:

I am planning to have a house built using the turn key method. Various companies I have approached quote certain u values for walls, roofs etc., and I am wondering if there is any measurement, like the blower door test for airtightness, that would confirm after building that these have been met.

What type of house are you considering Ginetta?

Mellor

AJL wrote:

The then worked out my heating load which is 9 kwh/m2y (is that right mellor!!).

Spot on Wasn't correcting you, just clearing it for the OP.
It's a very good value too. What does the total come to when water heating and electrics are counted too? Or is 9 the total. Nice figure either way. Les hope the BER certs will reward enviromental building with a good levels to meet.

AJL

Hi Meelor,

This is for heating only. Using solar panels to supplement hot water.

ratem

There are a number of issues that you need to consider before you build:

• Use a reputable company that will go through the details of the typical energy rating your house will achieve. It now has to be at least a B1 under the new regulation.
• Passive houses will cost about 10% more to build and save you 80% in energy bills over the current "C" rated house and will do that for each year you live in the house.
• If you have an option on your site orientate the house correctly facing South to get the most from passive sunlight and perhaps the options of Solar thermal heating or even Photovoltaic generation of electricity.
• The New building regs set out some new conditions which require the inclusion of a form of renewable energy and you will need to have the house subjected to an air pressure test.

But the direct answer to your question is this if you ignore the fine detail now the remedy is an expensive one and the benefits of getting it right are those you can enjoy for the rest of your time in the house.

PM me on this if you have any further need for advice.

Ratem

builditwell

I think along the way Ginetta's question became disected into peices

Perhaps the best solution is to employ an architect who will have experience in u values of construction products used etc , an engineer who will be able to verify this and a competent bulder who is able to complete the job to the required level under supervision of above so that the house performs to the u values specified .

Regards
Builditwell