Steel beam 9m span?

[justusandersson]

No no, everyone should join

No no, I didn't take it the wrong way. On the contrary, I think it's great that you have the time to write. I just think this is an opportunity for alternative constructions that reduce the heights and I know you master it better than I do.

An average U-value of 0.4 probably requires focusing especially on the floor. You can likely get glass sections with a U-value of 0.9 except for the sliding parts. It's important to minimize the requirements for the roof as much as possible.

 

[attefall]

Perfect, then you've gotten some value from the municipality at least Do you know which glass partitions you will purchase yet?

No no, I didn't take offense. On the contrary, I think it's great that you have time to write. I just think this is a place for alternative constructions that reduce the heights, and I know you're better at that than I am.

An average U-value of 0.4 probably requires focusing primarily on the floor. You can surely get glass partitions with a U-value of 0.9, except for the sliding parts. It's about reducing the roof requirements as much as possible.

An average U-value of 0.4 probably requires focusing primarily on the floor. You can surely get glass partitions with a U-value of 0.9, except for the sliding parts. It's about reducing the roof requirements as much as possible.[/QUOTE]

In the design that has been developed, they have calculated:
Roof (41.48 sqm): 0.132
Wall (12.5 sqm): 0.15
Foundation (41.48 sqm): 0.13
And assumed:
Windows (31.33 sqm): 1

This gives an average of ~0.35 https://www.wolframalpha.com/input/?i=(41.48*0.132+12.5*0.18+41.48*0.13+31.33*1)/(41.48+41.48+12.5+31.33)

If I insert an X instead of the roof https://www.wolframalpha.com/input/?i=(41.48*X+12.5*0.18+41.48*0.13+31.33*1)/(41.48+41.48+12.5+31.33)=0.4, I can see that I can have a maximum of 0.28 in the roof. Lowering the windows to 0.9 allows me to go up to 0.36 in the roof construction https://www.wolframalpha.com/input/?i=(41.48*X+12.5*0.18+41.48*0.13+31.33*0.9)/(41.48+41.48+12.5+31.33)=0.4

If I'm calculating correctly

EDIT: The window partitions are not ordered yet, since I haven't had the exact dimensions. But I think it's possible to get below U 1

 

[attefall]

If I insert an X instead of the roof [link] I can see that I as a max can have 0.28 on the roof. If I lower the windows to 0.9 I can go up to 0.36 on the roof structure [link]

Oh well, it seems like the forum encodes the links incorrectly so + disappears. The equations should be
Current: (41.48*0.132+12.5*0.18+41.48*0.13+31.33*1)/(41.48+41.48+12.5+31.33)

To achieve average 0.4 with 1 window: (41.48*X+12.5*0.18+41.48*0.13+31.33*1)/(41.48+41.48+12.5+31.33)=0.4
x=~0.283

To achieve average 0.4 with 0.9 window: (41.48*X+12.5*0.18+41.48*0.13+31.33*0.9)/(41.48+41.48+12.5+31.33)=0.4
x=~0.36

 

[bossespecial]

An average U-value of 0.4 probably requires focusing mainly on the floor. The glass sections can certainly have a U-value of 0.9 except for the sliding parts. The key is to reduce the demands on the roof as much as possible.

In the construction that has been developed, they have calculated:
Roof (41.48sqm): 0.132
Wall (12.5sqm): 0.15
Foundation (41.48sqm): 0.13
And assumed:
Windows (31.33sqm): 1

This gives an average of ~0.35 https://www.wolframalpha.com/input/?i=(41.48*0.132+12.5*0.18+41.48*0.13+31.33*1)/(41.48+41.48+12.5+31.33)

If I insert an X instead for the roof https://www.wolframalpha.com/input/?i=(41.48*X+12.5*0.18+41.48*0.13+31.33*1)/(41.48+41.48+12.5+31.33)=0.4 I can see that I can have up to 0.28 on the roof. If I lower the windows to 0.9 I can go up to 0.36 on the roof construction https://www.wolframalpha.com/input/?i=(41.48*X+12.5*0.18+41.48*0.13+31.33*0.9)/(41.48+41.48+12.5+31.33)=0.4

If I'm calculating correctly

EDIT: The window sections are not yet ordered, as I haven't had the measurements fully determined. But I think it can come under U 1[/QUOTE]

The calculations are surely correct In addition to this, one should consider thermal bridges. Typically, about 20% is added to the calculated average U-value. One can of course calculate the actual thermal bridges, but this is not done often as it might cost more than it's worth. An important thing to know about windows that are too good is that you risk condensation on the outside, especially on cold clear nights. So, if you don't want condensation on the outside, you should opt for "just right" windows. This doesn't quite align with energy efficiency thinking but is still something to keep in mind.

 

[Sharky58]

It says "Wall (12.5 sqm): 0.15" but in the formula, it says 12.5*0.18.

/Göran

 

[attefall]

The calculations are surely correct In addition to this, you should take thermal bridges into account. Typically, you add about 20% to the average U-value you calculated. Of course, you can calculate the actual thermal bridges, but this is not often done as it may cost more than it's worth. An important thing to know about really good windows is that you risk condensation on the outside, especially on cold, clear nights. So if you don't want condensation on the outside, you should aim for "moderately" good windows. It doesn't quite align with the energy efficiency mindset, but still something to keep in mind.

I'm not really sure if the current designer has accounted for the thermal bridges, I hope so; otherwise, it creates 20% extra problems...

But if we assume they have and that the values for the other parts are fairly accurate, it seems it should be possible to get a fairly thin construction with IPE120 or HEB100 beams and polyurethane insulation in between. I can imagine the thermal bridges will be significant, and therefore it's really beneficial to account for a 20% standard I need to learn a bit about how to calculate these U-values...
But even with steel beams and slimmer insulation, it probably still depends on having a maximum slope of 1:60...

 

[attefall]

It says "Wall (12.5sqm): 0.15" but in the formula it says 12.5*0.18.

/Göran

Thanks, it should be 0.15. So now I've already saved 0.01 thanks to you, which I can spend on less foggy windows

 

[Leif i Skåne]

Here are some more details regarding the anchoring of pillars anyway.

What should it be outside the glass partition? Should you trip on the rail every time you go out onto a deck outside?
Lower the glass partition to match the height of the rail's build height.

Check out post #19
https://www.byggahus.se/forum/threads/uterum-infaestning.304852/page-2#post-2839880

 

[attefall]

What should be outside the glass section? Should you trip over the track every time you go out on a deck outside?
Lower the glass section corresponding to the track's building height.

check post #19
[link]

Yes, you're absolutely right. I had planned that but forgot since my head has been full of other things.
You write "My lower track was 9 mm below the concrete surface," how do you practically lower it into the concrete?

 

[bossespecial]

Thanks, it should be 0.15. So now I've already won 0.01 thanks to you that I can spend on less fogged windows

Well, unfortunately, we're not just talking about a little fog The condensation that forms can freeze into ice/frost, and then it might be a bit hard to see out. Maybe not such a big problem down there in warmer latitudes as it is up here

 

[attefall]

Well, we're unfortunately not just talking about a bit of fog The condensation that forms can freeze into ice/frost, making it a bit difficult to see out. Maybe not such a big problem down there in warmer latitudes compared to up here

It's humid here all the time... but below freezing temperatures are much rarer
But is there really a big difference in how much fog forms between, say, 0.9 and 1.2? Much higher than that is probably unrealistic to get approved..

 

[justusandersson]

I think you should consider making the extension slightly less wide, perhaps 8 instead of 9 meters. Every meter in reduced span makes a big difference in beam heights. Moreover, which I actually think is most important, it's rarely successful to build extensions that are as wide as the original house. I haven't seen any perspective on the whole (house + extension) but I suspect I am right.

 

[attefall]

It would probably help to reduce the width, but it feels really tedious to search, wait, and pay for a new building permit..

I have seen it suggested to pull in the support beam slightly and have it in front of the glass section. In that case, it wouldn't be a problem to post 1/4 of the way in and halve the span. But how is it really with large glass sections, what is needed for their attachment? Is it reasonable to solve without having the support beam directly above?

 

[bossespecial]

I did some calculations on U-values just now. With the given conditions, you almost meet the requirement 0.40 with the addition for thermal bridges. If you instead increase the insulation in the floor by 100mm, the requirement is met and you can make the roof a little “worse” than suggested. U-value for windows assumed 1.0

 

[bossespecial]

It would probably help to reduce the width, but it feels really troublesome to search, wait, and pay for a new building permit..

I have seen it suggested to move the main beam slightly and have it in front of the glass section. If so, there shouldn't be a problem to post up 1/4 way in and halve the span. But what about large glass sections, what is needed for their mounting? Is it reasonable to solve it without having the main beam directly above?

It's not a problem to solve when you have a nice steel beam just inside.