Holdfast Training Services Trial Blog

Following a site mtg we have a much clearer understanding of the issue at hand. The mech contractor, Envar, have sent us a mark-up (as requested) of the location and sizes of all holes made by the builder to initially increase air flow; which it has.

So why are we not getting the correct RA flow to the AHU? It also came to light that there is heavy congestion (as shown in fig 1) around a services (namely ducting) choke point (about 1 m²) which is restricting the RA flow. The congestion issue is unique to this level due to the balcony which a severely reduced the overall free area by approx. 1 m². So, in theory we could turn the closest partition wall into a sieve and we would still have the problem. We can’t practically do this though as there isn’t enough space in this particular partition.

Therefore, we still need to get the balance of air from somewhere which the AHU fan is drawing in. So with the choke point in mind this will have to come from the SA side (the corridor) outside the plantroom. This corridor is open to the large open-plan office area but air flow either end is stopped by pneumatic actuated doors (for security as these areas are sub-tenanted). So what? The makeup air would be mostly SA and not RA as intended. So how does this affect the CO² levels?

Below I’ve recalculated the area of hole required which would be incorporate as either a door grille in the plantroom door, or, depending on size, it could turn out to be a complete louvered door.

Figure 1. Return Air Choke Point in Plenum.

Calculations

A quick calculation to check the hole size required:

Q = 8.839 m³/s. This is the entire SA flow rate that is trying to get back to the AHU as RA.

A = 1 m². The approx. area of free flow through the choke point.

Therefore, V = 8.8 m/s. That’s pretty quick and why it has also been reported that a few ceiling titles are flapping around near the exit hole from plenum into plantroom. These are being addressed by replacing with egg crate extract grilles.

If we want to achieve a steady flow rate of 5 m/s then this gives an A = 1.77 m². Subtract from that the area we do have (1 m²) = 0.77 m² hole required.

On a basic 2100 x 920mm door (leaving an edge of 100mm both sides) gives a door grille neck dimension requirement of 1100 x 720mm = 0.79 m². That’s the ‘free air’ area needed where a louver or grille would require being 50 – 60% bigger to take into account the area lost due to the vanes. So, it would need to be 1.26m², which is about 1800 x 720 = 1.29 m² which equates to pretty much the entire door when you take into account the structural edges.

So what? It would require attenuation on the plant side of the door to mitigate plant noises transferring back into the corridor, which shouldn’t be heard too much anyway as it is just a corridor and the open-plan office area is actually through a central kitchen/restroom area.

To check this I spoke to our acoustic engineer and used the dB data. The corridor was reading 52 dB, I then added 25 dB for removal of the current door and then subtracted 5 dB for adding a louvered door with some attenuation on the reverse side. This results in 72 dB being heard in the corridor, which is about 22 dB over what it should be (50 dB being the norm). Therefore, this is a problem and exacerbated by the frequency range of the particular plant, which will be a low rumbling (low freq) which louvers still let through.

It would therefore be better to install an ATD above the plantroom door but this idea was discarded due to a large duct run right next to it running down the length of the corridor. This also means that we can’t put any more egg crate extract grilles in as the one currently installed sits no more than 10mm below the ductwork so this too will be restricting the RA.

The only other option I can see is putting in a large or two smaller ATDs through the wall area into the plantroom. But even this has its issues: is there free space on the other side of the wall? How far away is the AHU and can we fit a ATD in? Being the base build, will the building owner approve it?

I have also been informed the AHU has an economy cycle (which I should have expected) where the ambient OA temp dictates how much OA is used rather than wasting energy in cooling RA when there’s ‘free’ cool air available from outside.

ATDs

I made a point of mentioning the need for ATDs in the cut-outs. With the extra holes present no occupants have complained of cross-talk, therefore Envar suggested they would get the builder to tidy-up the holes and leave them at that. Ironically, it seems like any holes made in the partition wall don’t need attenuating due to the ductwork congestion.

Introduction

Prior to Christmas I was given an interim task to investigate complaints of doors being hard to close with loud whistling noises coming from the plantroom door on level 4. The project is a typical tenancy office fitout with construction complete and the office space occupied by Synergy staff.

I was given an initial steer by the project leader; his view being restricted Return Air (RA) flow to the AHU.

Background

The design of the floor (slab to slab) uses the ceiling void as a large RA plenum. The plantroom, containing the AHU, acts as a large mixing chamber mixing the RA (from the plenum) with the Outside Air (OA), which enters through louvers in the skin of the building. It incorporates a CO² monitoring system that controls the motorised louvers to alter the amount of OA required to keep CO² levels within permissible limits.

The main floor space is split up in to a number of offices (various sizes) and larger open plan areas. To reduce the chance of cross-talk between these areas full-height partition walls were constructed. Whilst this met the acoustic requirements it created a subsequent problem; the RA was being severely restricted in its attempt to get back to the AHU.

To resolve this, the design incorporated the use of Air Transfer Ducts (ATDs) installed through the partition wall. ATDs are essentially fitted into a rectangular cut-out in the wall and consists of standard metal ductwork lined with acoustic material. This allows both air flow through it and simultaneously reduces carried sound, as shown in figures 1 and 2.

Figure 1. Basic ATD with Acoustic Lining.

Figure 2. ATD in Use.

Identified Issue

A typical problem found in RA systems, that utilise a plenum rather than a ducted system, is not enough RA finding its way back to the AHU. In this case the number of installed ATDs is insufficient to allow the correct amount of return flow and is creating positive pressure build-up. Effectively, the mixing chamber (entire plantroom) is being starved of its required RA (under negative pressure) and the CO² monitoring system, not seeing excessive CO² levels, won’t allow any more OA in. Therefore, the only available air remaining is from outside the plantroom in the corridor (which is under positive pressure) and is now being sucked (willingly) into the plantroom and creating excessive whistling noises. Figure 3 shows a basic sketch I drew to aid in visualising the situation.

Figure 3. Situation Hand Sketch.

What’s possibly exacerbating the issue is the CO² monitoring system. Because the RA is being restricted the CO² monitor is most likely reading low CO² levels, therefore signalling to reduce the OA intake as it’s not required to dilute the RA. This then creates increased negative pressure inside the plantroom and thus makes it easier to pull in air from the corridor due to the AHU fan demand. It then become a vicious circle as this extra air being pulled in from the corridor is most likely to come directly from the SA grilles, with little human traffic, meaning the CO² levels will low.

Depending on how much the RA is restricted will determine the severity of the symptoms found.

During construction there were a number of design changes, doors being relocated and the like, which caused the air flows to change slightly. This however, is not deemed a significant reason for the symptoms being experienced.

Resolution

The resolution quite simply requires increasing the number of air passages through the full-height walls. As stated this had already been designed for and implemented through the use of 5 No. ATDs, however, clearly more are required. Figure 4 shows the drawing mark-up with existing ATDs (blue) and my proposed design for additional ATDs (pink).

Previous Resolution Attempts

The mech contractor had already attempted to solve the issue by cutting holes in certain locations within the full-height walls. While this may have helped to alleviate the issue, it has not solved it.

Figure 4. CAD Drawing Mark-up.

Design Calculations

I conducted some basic calculations to determine the number of ATDs required, allowing the same rate of return air flow as that being supplied to the floor space, resulting in a more favourable neutral pressure.

The calculations included splitting the floor space into sections, boundaries based on the full-height partitions, where I then added together the SA from each diffuser in that section. I then worked out the area required (using Q = A x V based on a 5 m/s air velocity) to get that flow rate through the wall to the next section. I continued the same calculations for the other sections, remembering to carry through the flow rate from the previous section as the RA from the entire plenum space is trying to get back to the same point (left to right when viewing the dwg).

In total I calculated an additional 9 No. ATD2’s (600mm x 400mm) were required. In truth it’s only the cut-out dimensions that are actually required to solve the air flow issue, not the ATDs per se.

Design Considerations

There are important factors in positioning ATDs within a plenum: availability of space between the upper floor slab and false ceiling, space between other services, and understanding the use of the rooms either side of the full-height wall to name the most important. All these were considered in my design. The last consideration, the use of rooms, is particularly important as this could determine the possibility of negating the need for ATDs in a particular location altogether. That is not to say there wouldn’t be a cut-out, just no ATD installed, so still allowing the required passage of RA.

COAs

Two COAs were considered, with time, cost and quality in mind. However, before the suggested COA is carried out a number of RFIs must be answered by the mech contractor, these are: confirmation of the location and size of previously made cut-outs, and an estimate on the availability of space to install the ATDs. The location and size of previous cut-outs is important as these could be utilised and potentially increased, based on the calculated sizes above, as suggested in the COAs below.

COA 1

This would be conducted in two stages, both during out of hours so as not to disrupt staff working:

Stage 1 – Make the cut-outs in the full-height partition walls as indicated on the mark-up drawings.  This should solve the issue, however may lead to excessive cross-talk.  If the room pressures have been restored, the symptoms disappeared and there is no detection of cross-talk, or it is at an acceptable level, then the works will be complete.

Stage 2 – Assess the level of cross-talk, if it is not acceptable then conduct stage 3.

Stage 3 – Install the ATDs in the designated cut-outs, thus solving the cross-talk issue.

Pros and Cons

The main pro is: If stage 1 is sufficient there will be a substantial cost saving on negating the need for possibly all or at least some of the ATDs; each approx $1000 a piece depending on size.

The con is: If stage 2 is required then there would be extra labour costs due to the mech sub-contractors having to go back a second time to install ATDs.

COA 2

Do as COA 1 but all stages in one go.

Pros and Cons

The main pros are: Reduced labour costs for the mech sub-contractor and all the work being done in one go means minimal disruption.

The con is: The ATDs may be superfluous in solving the issue and therefore present an unnecessary cost.

Noise Level Consultation

I discussed the issue with our acoustic engineer and am confident that the overall cheapest option, that still achieves the required acoustic quality levels, is COA 1. This is based on not all the positions identified requiring ATDs. The exact number cannot be confirmed until a further assessment is conducted post stage 1 of COA 1.

Recommended Solution

The recommend solution is COA 1 but I envisage having to discuss these actions with the mech contractor, as alluded to, to get answers to my RFIs. This may also involve going on site to discuss further.

Update

During the preparation of this blog I learnt, through a third party, that the mech contractor indicated it wouldn’t be possible to fit the ATDs as proposed due to lack of space in the partition wall around the plantroom. There were some other suggestions mentioned, such as, installing a large transfer grille in the corridor/plantroom wall but this would need to be quite large to solve the issue and would likely look pretty rubbish not to mention noisy. It would then require an attenuator on the plantroom side to attenuate the plant noise. I think the next step is to meet with the mech contractor to discuss options.

What did I learn?

A key observation, which extends to all projects, has been that no matter who you ask for advice, you will always get a slightly different answer. The key principles will be the same but individual engineers’ will be basing their ideas on their accrued experience. I suppose this highlights the meaning of engineering, derived from the Latin ingenium, meaning ‘cleverness’ and ingeniare, meaning ‘to contrive or devise’, and just goes to show there is more than one way to skin a cat. The challenging part is to learn how and why these little design nuances can aid in delivering a more technically, sustainable and economical solution and therefore aid in refining your design skills. The technical solution also needs to be balanced with any political considerations, especially when wishing to win any future work with the same client.

I also learnt about the disadvantages of plenum based return air systems and found this article helpful in understanding:

http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwjxgbbF9NzKAhVELg8KHbM0CyEQFggsMAI&url=http%3A%2F%2Fbookstore.ashrae.biz%2Fjournal%2Fdownload.php%3Ffile%3D2015Mar_044-047_EngNote_Taylor.pdf&usg=AFQjCNFMBmRONuxPkHoOOQXtChymqc4RJA

In Other News

I organised a surprise birthday present for the wife; a great view of Perth from 1500ft. It included a shot of JHG’s PCH project and the new sports stadium, managing contractor being Brookfield Multiplex (new alternate Ph2 attachment). I’ve also included a few other snaps…

Perth Children’s Hospital.

Perth’s New Sports Stadium – Still in the structural build stage.

Perth’s Central Business District.

WA Coast Line.

Happy Wife Happy Life!

Original article written for Sapper Mag:

On Sun 31 Jan 16 members of the Professional Engineer Training (PET) course embarked on the ultimate test of civilian toughness – Tough Guy 2016. Four elite members of the cohort were selected to compete; Captains Grant, Kiddie, Palmer and Parton had trained for literally hours and were in peak physical and mental condition as they journeyed over to the exotic lands of Wolverhampton for the event.

For those unfamiliar with the Tough Guy Concept the event calls for competitors to cover 15km of cross-country running interlaced with wet and muddy obstacles and hill sprints. The theme for this year was “The Somme” with the course culminating in an obstacle course named the ‘Killing Fields’ with electric fences, burning hay, concrete tunnels, a lot of cold water and endless mud.

Morale remains high for Kiddie and Grant. 

The ‘Toughened’ PET team celebrate.

Unfazed, the team donned their lycra, neoprene hats and X-Country trainers and fought their way to the front of the 3000+ people starting the race. At the starting cannon the team was immediately split into two groups and ran hard to get to the front of the pack; myself and Capt Parton found ourselves in a group of crazy Germans and Danes who remained with us for the rest of the event.  The next 10 miles blended into a haze of throbbing legs, ice-cream headaches and a lot of bruises.  Particular highlights of the course include seeing a fellow competitor dislocate his shoulder, a series of twenty 50m hill-sprints (some carrying a car tyre) and an alternating ditch-hurdle arrangement called the ‘Gurkha Grand National’.

Special mention is due to the commitment of Fred ‘the tank’ Kiddie who was running the race as part of his first weekend as a married man, fuelled only by a bottle of Lucozade and propelled by a pair of inadequate flat-soled CrossFit trainers. Also credit is due to the old man of the group, Capt ‘Eton’ Grant, who was competing on his 32^nd birthday and only managed to get round as he was following a young lady dressed as a bunny girl (whom he followed from Mile 1).

The team conquers another obstacle within the ‘Killing Fields’.

Three hours later the last of the PEW cohort had made it through the finish-line. Two of the group had finished in the top 150 runners and the team average time was in the top 25% of the field … not too bad for a group who spend most of the week in a classroom.

Thanks are due to Mid Kent College and 1 RSME Regt for supporting the team and allowing them to make such a good effort. Lastly, for anyone brave enough to take on the Tough Guy challenge next year a few tips; issued builders gloves are a must, neoprene hats are advised and more than two pints the night before should be avoided!

Capt Mark Palmer RE

Yesterday I attended a PIANC workshop at the ICE. PIANC is the International Navigation Association, the body that produces codes for ports and waterways and governs much of what I am doing during Ph3. Coincidently, the chairman of PIANC works for CH2M.
The day focused on the ‘future of design’, challenging and refining codes, and expanding design in to new areas such as seismic (previously not covered).
In parts, the technical aspect when straight over my head as I lacked decades of practical experience however, some of the key takeaways for the day were completely generic across design disciplines.

Some generic points:

Updating of codes – M/515 (Extending the scope of Euro Codes)
There was a public acknowledgement that the updating of ENs due was overly complex, poorly publicised and understood. The main concern were the pending changes (M/515) to load factors, partial and combination factors across all areas of design.

Code Bashing
There is a concern that code writers have become wrapped up in code-bashing. For instance, the ψ (trident for Brad) factor, in ENs is used for long term effects such as creep. So why is that factor appearing, in the same context, in codes dealing with seismic design…surely the impact of the ground accelerating back-and-forth is far worse than a little creep. PIANC are attempting to identify these cases and add clarity/remove confusion within their own codes. They are also offering their finding to the EN and BS committee’s but acknowledge that changing principle codes will not be easy.

The legal requirement of codes
ENs use the would Shall which legally implies you must do it. BSs use Should which implies a recommendation but is supported but an understanding that without just reason or better knowledge it should be considered as shall. The bottom line and advice from PIANC was to treat these as the same ‘a legal requirement’ and only challenge the code if you undertake some form of monitoring, statistical or physical modelling during the design phase.

BIM
Not a single engineer present (over 100 from a wide range of companies) had used BIM for any non-government project. Furthermore, when asked to what degree it had been utilised for Gov projects, only sniggering could be heard. There is no doubt that if used correctly BIM is a fantastic data managing tool that would support the H&S/project files etc. However, this is not happening. The key concern is that as-builts are improving but supporting cals, assumptions, etc are not available which makes future alterations difficult. PIANC is attempting to manage this by introducing the requirement to produce a ‘Facilities Operating Manual’. In essence the factors and design assumptions made at every step of design are to be logged and presented with the drawing pack. This is not optional if designing to their codes. It does not require companies to expose their calcs or software details but an understanding of inputs and outputs along with factors.

Summary
The day highlighted a genuine desire across the industry to refine the policies and the codes in use. The senior PIANC committee were open and seemed active to explore ideas being presented to them rather than trying to justify their latest publications. There was a acceptance that the ENs are so vast that using them as a baseline and working alongside was the most proactive way to progress rather than trying to alter, amend or refine them. The day finished with a short discussion on what, if any, new codes should be written.

Genuinely a good day that expended my understanding of how the codes are born, developed and published. It was warming to see that the industry steers the codes and is not simply constrained by them!

Does anyone have any recommendations for a sensible c’ for a soft sandy clayey SILT?

I’m thinking I’ll probably assume something around 5, then bash out a quick sensitivity analysis to see how much difference it makes to my foundation design then make a decision based on risk.  But I’d be very happy to hear if anyone has experience in this sort of thing?  – Damo I’m looking at you, and John obviously!

“Believe me, my young friend, there is nothing – absolutely nothing – half so much worth doing as simply messing about in boats.”
― Kenneth Grahame, The Wind in the Willows

My other day out of the office was prompted by a letter from the Environment Agency to FirstPort property services stating that the concrete defences along the river Thames were damaged and needed repairing.

FirstPort did not know it was their responsibility to look after the defences. It turns out they got the management contract for the development from Berkley homes who built it. This particular detail was in the documentation but no one at FirstPort noticed it. So it was a shock to them when they received the letter in the first place.

The quayside in question is on the site of Brunswick PowerStation (think Battersea cut in half lengthways). The quayside was built in 1948 and therefore designed to the DSIR code. I was chatting to John about this yesterday and the code is so old it even pre-dates him! The code didn’t really take environmental factors into consideration and so the concrete cover to the steel is as low as 35mm. EC2 would say it must be a minimum of 65mm. Additionally these large public projects in the post-war years were a good way of employing soldiers returning home after the war to a weak economy and high unemployment. So soldiers would be given jobs on construction sites, this one included. Their workmanship was a bit dodgy as was the compaction methods of the time meaning the concrete is not as dense as you would expect from modern methods.

Then…

…Now

The combination of little cover, poor compaction and an aggressive environment has resulted in some fairly substantial corrosion to the steel. Chlorides in the environment penetrate the concrete and the steel corrodes. The corroded steel has a high volume than the original steel and therefore cracks the concrete. Which lets in more water and the corrosion starts again. It’s a vicious cycle.

So we hired a boat and a concrete cover meter and went and had a look.

It is repairable. The problem is that it’s going to be an ongoing maintenance burden which will ultimately be paid for by the residents through their maintenance fees. The bill for this will be over £100k, which split over all the properties in the development is not a huge amount of money, but if they have to do significant repairs each year – which they might – the residents are going to get pretty tired of it pretty quickly.

I’ve got to go to a residents meeting there in a couple of weeks to explain this to them all. Not looking forward to that!

I’m back!

After some weird issues regarding my account, I can now post blogs again albeit I’ve had to get a new account linked to my work email in order to do so.  So when I’m finished at WYG we’ll have to try and set up another account on my personal email so I can continue to see the blog – one for Jim to ponder…

Anyway, about three weeks ago I managed to get out of the office for two days.  One day I spent on the Thames on a boat – more on that later.  The other day I spent in a field.
I’m designing a couple of crossings over high pressure gas pipelines to provide access for vehicles into a quarry.  You may have seen my previous blog where I was tearing my hair out over the vehicle loading.  A number of site investigations had been completed previously but had focussed on the agricultural or quarrying value of the site.  None had collected any geotechnical properties and I need them to complete the design.  So I organised a local Geotechnical engineer to go along and do some boreholes.

I got there to find two blokes (the rig operators) stood by the side of their vehicle, looking at the farm land which is the site, shaking their heads.  I said hello and they said “We’re not going on there”. Good start.  It was a bit wet, I accept that, but what was he expecting?!  The engineer turned up shortly after and we walked the site while we waited for the National Grid bloke to turn up.  In order to plant a daffodil within 15 meters of a high pressure gas line you need National Grid to send an engineer to observe.  I wanted the bore holes as close to the location of the crossings as possible, obviously.  The rig operators didn’t want to go onto the field.  Their argument was that it was too wet and the rig would sink.  I really doubt it would of, but I was never going to win that one, so we came to a compromise.  We selected locations for the boreholes that were on the firmer ground at the edge of the field.  This meant that the locations were now more than 15 meters away from the gas pipe and therefore the gas man had driven for 3 hours to get to us only to find he now no longer needed to be there.  He checked the locations, gave me a piece of paper saying it was all ok and then left, shortly followed by the Geo engineer who let his rig team get on with it.

John previously said that once you see a drilling team do their thing you’ll never trust any of their results ever again. I now agree…

Let’s take N values as an example.  The book (CIRIA R 143, among others) says that to get an N value from an SPT you hit the stick with a weight and measure the number of strikes to move the stick 300mm (very simplistically).  The report also states that poor operator technique can produce disturbances in the soil below the head that then leads to unreliable results, especially in granular materials, the bigger the particle size the bigger the effect. I’m working in gravel. Oh good then!

I watched the crew conduct an SPT at around 4.5 meters’ depth.  They drove the collar to about the depth they wanted and lowered a weighted tape down the hole to measure the depth.  But they didn’t measure the amount of collar sticking up out of the ground and so don’t know the difference.  The point with SPT is that the material is undisturbed.  If you don’t know the difference in level between the bottom of the collar and the test level, how can you possibly estimate the amount of material that has fallen from the sides of the hole?  And this is a particular problem in large particle rounded non-cohesive soils like gravel.

The operators then introduced the rod into the hole and drove it “for a bit”.  Not the stated 150mm seating drive.  Additionally, BS 1377 states that the seating drive should be limited to 25 blows.  I must admit I wasn’t counting, but I’m not confident it was.  They then got a stick with some lines on it, held it against the rod and drew chalk lines on the shaft (cue Brad giggling) where the lines were (at about 75mm intervals).  They then drove the rod noting how many blows it had taken to reach each line – or there about.  The lines weren’t exactly straight but at this stage that was the least of my concerns.  The operator then wrote all this down in his book and made a cup of tea while his mate changed the head over.

The crew also took samples at various depths including both the gravel and the underlying clay, which they did pretty well from what I understand.  They put the coarse-grained stuff in bags and for the cohesive soils the sealed it in wax to keep the water in and treated it pretty carefully.

So what?

So I’ve got some N values and I’m awaiting the lab test results.  Do I weight the reliability of the lab test results against the N values since the method of collection looks dodgy?  No.  There are loads of other factors that affect the accuracy of the N value including the stiffness and exact diameter of the rod and the angle of drive, but I didn’t measure them. So who am I to judge?  The factor of safety applied to the results is there for a reason and as long as I try to triangulate the properties with the lab results and anything else I can find I’ll crack on and use them.  I’ve got nothing else so I need to use something!

Go on then John, I’m braced!

Stay tuned for… “Messing about on boats”

This week has been my first real foray into Revit and the force is not strong in this one. Below is the product of 2 days of hard fought CADing; it’s a good job I’m not billed out by the hour! The model is the ductwork and Fan Coil Units (FCUs) in the accommodation element of the NCO Academy. Blue is supply, Orange is return and green is exhaust.

All the duct work is sized using my new friend the ductilator. It certainly makes the tiresome job a lot quicker and easier than calculating them mandraulically! The flex duct connectors at the ends are basically cheating. However, as we have only just exited the 35% gate I’m sure there are plenty of movements to come and these allow elements to be moved independently without Revit dropping its fill. This is especially true as the zoning of the interstitial space has not been worked out yet. As appears to be commonplace we are waiting on structural to finish overdesigning beams before we can get into the important work of cutting holes in them.

On a more serious note the building was originally conceived, presumably by the architect, as being 18ft floor to floor. Ignoring the training room, and its 12ft ceiling, that will no doubt be the subject of a blog in the future; the remainder of the rooms had a mixture of 9ft and 10ft ceilings. This translated to a 9ft interstitial space in some of the rooms, something which laboratories would be proud of. Arguments about leaving it alone were that the cost of brickwork wasn’t much when weighed against the time, and therefore cost, of trying squeeze everything together. My counterargument was sustainability bringing a big fat tick in the E3 box. I was thinking of the carbon output but to translate it into ‘American’.

To back this up I did some very rough calculations in Carrier HAP (Hevacomp equivalent) which showed that on a summer design day the cooling load would reduce by 2.8% and on a winter design day the heating load would reduce by 7.3%. Sadly, due to the way LEED savings are calculated this doesn’t translate into extra points for design, however it is good for life time running costs.

So the compromise is set to dropping the floor to floor height to 16ft which, across both floors, saves 4ft. The negotiated allowances for each discipline are shown below, though the electrical engineer has agreed to let HVAC enter his cable tray allowance and he’ll work around it; sensible. Everything is conservative at the moment so maybe we will be able to shave a little more off. Although clearly the model is getting ever busier and so unless the height savings are significant I shan’t hold my breath.

In other news I’ve found someone else that uses John’s calculators.