When is a cold bridge a cold bridge?

[SimonD]

So, I've been playing around with my new thermal imaging camera around my house, and randomly pointing it at parts of the house. I'll do it properly over the next few days when I have some more time. But there were some interesting findings.

 

From the outside my thermal envelope looks good, no obvious thermal bridges but I can actually just see the ewi anchors even though they're thermally broken. However, when I pointed towards my yet to be insulated plinths, it was warmer than the ewi, not by much but it was noticable. I then went inside and noticed that the junction between the suspended timber floor and wall was colder on the brick side. Bear in mind I only have 3 small rads heating the downstairs, but the exterior walls measured above 18C as did the main floor. At the junction the temp drops to 14.2-14.5C at its coldest. This is retrofit so these wall and foundations all existed before and I do have insulation extending below the floor at the walls by 150-250mm below the joist where there is the room above the over-site.

 

Looking up information on this, Passivehaus International mentions that the problem is where the temperature falls below 12.6C as this is when mould could form. I'm obviously above this and when I actually have full heating, there will be improvement.

 

What's the view here? Should I hang my head in shame about this, or is this acceptable on a retrofit?

 

And can anyone shed further light on what is typically deemed to be a problematic cold bridge?

Edited January 31, 2023 by SimonD

[joth]

33 minutes ago, SimonD said:

Looking up information on this, Passivehaus International mentions that the problem is where the temperature falls below 12.6C as this is when mould could form.

That's a curiously precise number.

I'd say the problem is at the temp where condensation starts to form, and then mold is one possible consequence. Condensation is a function of RHI and internal air temp, but sits a bit nearer 15°C in our house.

 

[tuftythesquirrel]

2 hours ago, SimonD said:

What's the view here? Should I hang my head in shame about this, or is this acceptable on a retrofit?

Certainly not, it's great practical feedback on how the building technology is working. At least you are aware of the concept, which is a good start. People (other builders) thought I was nuts when I chopped off the protrusions from our steel roof trusses that were punching a big hole in the insulation, prior to fitting the EWI. Glad I did. It would be nice to see some pics. (Got thermal imaging camera envy).

Edited January 31, 2023 by tuftythesquirrel

[SimonD]

1 hour ago, joth said:

That's a curiously precise number.

I'd say the problem is at the temp where condensation starts to form, and then mold is one possible consequence. Condensation is a function of RHI and internal air temp, but sits a bit nearer 15°C in our house.

 

 

Yes, it is isn't it. Reviewing the small print it says @ 50% RH. Will have to see how it goes with us and keep some records of temps.

[SimonD]

1 hour ago, tuftythesquirrel said:

People (other builders) thought I was nuts when I chopped off the protrusions from our steel roof trusses

 

Well, my architect designed this beam to be essentially sat in a stud wall that was the thermal envelope ! I changed the design, moving the wall outside so the beam's now fully inside the thermal envelope.

[IanR]

In PassivHaus terms a thermal bridge is any junction that has a calculated Psi value higher than 0.01 W/m.K. For my frame we tried to work on having a minimum 2/3rds of the nominal insulation thickness in the tight areas, but did have to drop to 50% in a couple of places. Calculated Psi values were still below the target.

 

In standard building regs terms I believe a cold/thermal bridge is when it leads to a risk of condensation on the inner wall ie. the inner surface of the wall dropping below dew point. 21°C air at 65%RHI has a dew point of 14°C. Mould growth doesn't actually need condensation, just an RHI of +80%, but it does need those conditions to persist for a period of time (days). 

[ToughButterCup]

4 hours ago, SimonD said:

..,.. typically deemed to be a problematic cold bridge?

 

It's whatever the nearest woman says it is.    

Me coats almost on ..... byeeeee

[tuftythesquirrel]

22 minutes ago, SimonD said:

Well, my architect designed this beam to be essentially sat in a stud wall that was the thermal envelope ! I changed the design, moving the wall outside so the beam's now fully inside the thermal envelope.

Good work - easy to rectify at the design stage - good job you didn't build it 😁

[SimonD]

16 minutes ago, ToughButterCup said:

 

It's whatever the nearest woman says it is.    

Me coats almost on ..... byeeeee

 

You have now hit on the ultimate authority 😁

[Radian]

5 hours ago, SimonD said:

So, I've been playing around with my new thermal imaging camera around my house

This thread is worthless without the pictures 😁

[ToughButterCup]

When I played with mine I learned that I needed to 'tune' it really carefully to make the best use of the results.

 

It was very surprising to see my own  heat signature reflected by the glass in the window infront of me.  I could tune that distracting information out by altering the sensitivity range of the sensor.

 

 

 

[SimonD]

1 hour ago, ToughButterCup said:

When I played with mine I learned that I needed to 'tune' it really carefully to make the best use of the results.

 

It was very surprising to see my own  heat signature reflected by the glass in the window infront of me.  I could tune that distracting information out by altering the sensitivity range of the sensor.

 

 

 

Yes, I'm finding this to be a bit of a process. Mine auto tunes the temperature range, which means that it can transform the image from what looks really cold to what looks really warm, until I then reference the temperature range, so I need to play around with the settings a bit as I can create profiles to use for specific jobs, including add the emissivity value of the materials in question - e.g copper doesn't show very well at all on the standard.

 

As you say, windows are interesting as I get a 'hot' image of me reflected in the window, but the temperature shown in the display is the temp of the glass??? Pic added below.

 

I'm also getting what seems like some kind of bleed around the edge of the image at certain angles and distances.

 

2 hours ago, Radian said:

This thread is worthless without the pictures 😁

 Oh, alright then 😁

 

Random take along back wall. It's interesting how it shows the warmer line along the bottom of my ewi which is the stainless steel bottom rail, then a cooler section which is the plinth insulation and then warmer ground.

 

Front bay ewi showing much warmer plinth where I haven't installed the plinth insulation yet, but also that to the left, the boundary wall and bushes are are much warmer:

 

The front door. It's insulated accoya but as it's 1.2m wide, it required a steel reinforcement frame. That's clearly what's visible within the door. The dark area at the bottom is aluminium threshold and the shadowing down to the right, looks just like a pocket of cold air I assume as it's the uneated part of the house. Who knows??

 

We have a bridge using steel columns coming out the back of the house. These columns pass through the insulation layer. Even though they've been wrapped with eps and expanding foam within the thermal envelope I want to see if there's anything bad there. I can still add some insulation inside if there's a problem. The bridge bit is the one showing 5.7C:

 

 

The thermal store and pipework (yes, pipework still to be insulated). I think I am going to add some extra insulation around the cylinder :

 

 

Thermal selfie in window showing my body heat but also showing the glazing temp:

 

Edited January 31, 2023 by SimonD

[SimonD]

And some more:

 

Upstairs rad with Opentherm doing its job:

 

 

Flow temp:

 

 

Return temp:

 

[gc100]

Excellent. What’s camera is it?

[Radian]

1 hour ago, SimonD said:

Thermal selfie in window showing my body heat but also showing the glazing temp:

 

More like a reflection of the internal temperatures. If you wanted to measure the actual surface of the glass you can stick a piece of matt black electrical tape on it and image the tape.

 

Great work with the pictures and analysis. Your thermal bridge bridge is a tease though. Even if you wrapped the entire steel it has to terminate somewhere - higher ground?

[NandM]

On 31/01/2023 at 16:10, SimonD said:

 

Well, my architect designed this beam to be essentially sat in a stud wall that was the thermal envelope ! I changed the design, moving the wall outside so the beam's now fully inside the thermal envelope.

@SimonD - what do you mean when you say you moved the wall outside? Was this beam meant to have supported a wall directly above, but you re-engineered it work differently? I have three such beams (supporting external walls) and am looking at options to remove the cold bridge.

[Post and beam]

I would still like to know what make & model the camera was.

[SimonD]

8 hours ago, NandM said:

@SimonD - what do you mean when you say you moved the wall outside? Was this beam meant to have supported a wall directly above, but you re-engineered it work differently? I have three such beams (supporting external walls) and am looking at options to remove the cold bridge.

 

If you look at the below picture, you'll see the knee stud wall fixed to the top of the steel which also supports the glulam beams with the triple studs. This was designed to be the external wall by the architect. As you'll see from the picture, there is an additional stud wall behind. This is my redesign. This new exterior wall sits on my roof joists just behind the steel. Hope that makes sense.

 

[SimonD]

7 hours ago, Post and beam said:

I would still like to know what make & model the camera was.

 

Oh, I missed that. You're very patient. It's a Topdon TC001. I've now been using it for over a year for work and it has been invaluable for diagnosing and fixing heating systems and boilers.

[Post and beam]

I just googled it. So it works in unison with a smartphone as the display. Cool. If its given you a year of good service i'd say Bargain. Thank you