Anything that is hidden and out of sight is often out of mind too. And this might be true for ducting and insulation systems in a building. Poor duct connections and lack of insulation can result in too much energy consumption, eventually leading to high electricity bills.
Additionally, faulty duct lining can hinder the flow of air that moves through the building . Over a prolonged period of time, wear and tear of the duct lining may even cause blockage. In such situations it’s best to replace the entire ductwork insulation system. Some of the other problems with an uninsulated duct system are duct condensation, hot and cold rooms, and uneven temperatures. Adding insulation is the best method to fix duct temperature loss. However, one must be aware of choosing from various insulation options, as not all insulation types perform consistently.
MEP Middle East organised a roundtable and invited experts to discuss such issues. The participants were Abdul Hameed, sales manager, Faisal Jassim Group; Anil Mishra, manager technical specifications, MEA, KIMMCO; Paul Groves, business development manager, Khansaheb Industries; and Sunil Nair, project controls – technical lead, BK Gulf.
Mishra began with the basics by explaining the role of ducts and insulation. He said: “Ducts basically provide the means to transport air from the point of origin which is your fan coil unit (FCU) or an air handling unit (AHU) to the point of discharge, which is probably a room. It’s just a means to transport air. Insulation, of course, plays an extremely important role in energy savings because you got heat transfer, as metals are good conductors of heat and electricity. There is obviously going to be temperature rise in the air stream. The temperature rise in air stream at the point of terminal would not yield the desired air temperature, which means the air-conditioners have to work harder or more, which affects the energy consumption.”
On the subject of energy savings, Groves produced some numbers to the participants. As per Aecom, up to 50% of a building’s whole of life cost is MEP and up to 60% of that is HVAC, and so, ductwork is a huge component. Groves said, giving an example of his company’s ductwork product Spiralite: “Up to 58% [was saved using Spiralite], but that’s an extreme example; typically 25% to 40% energy can be saved. But our latest two projects here in the Gulf has been a 27% saving and 38% saving. So there are a combination of factors.”
KIMMCO, which has been involved in insulation for last 40 years, and which has done lot of energy audits across Kuwait, has been commissioned by the authorities in Kuwait to come up with some of their own figures. Mishra added by providing some of these figures: “When we talk about insulation, we don’t talk just about HVAC, we talk about the entire envelope. We have done some audits and found out that around 30% of losses is through ventilations, without insulation. Around 37% is through uninsulated heat loss, 24% is through windows, 3% is through basement floors, and 6 to 7% is through roofs. Now, when we insulate the entire envelope, with proper insulation, selections and R values, it is found that the heat losses are reduced by about 70%. It relates to 46% of annual cooling loss. And normally the payback time from a non-insulated to an insulated building is about 1.7 to 2 years, in terms of running costs. They have done a proper audit of this and found that a well-insulated building means a saving of approximately 1000MW per year. From uninsulated to insulated, it will give you savings of almost 1000MW per year, which translates to one power plant in every 9 to 10 years, with the growth of population.”
Nair brought the conversation back to ductwork by saying, “I can’t think of these kind of savings by doing ductwork insulation.”
Mishra’s said that over a non-insulated duct to an insulated duct, “you would save about 30% of energy consumed”.
Sunil Nair, project controls – technical lead, BK Gulf
Proper insulation for savings
However, Nair believed the percentage to be much smaller. He said: “If 60% of the load is mechanical, I would expect the load to be consumed by chillers, pumps, etc.” According to Nair, it’s the leakage factor that needs to be considered because you lose air through the ductwork.
He said: “Every material has got an insulation property. When we design within the constraints, we decide how much of a factor we should give for insulation. Whichever insulation you use, the thickness varies, it could be 13mm, 20mm, or 25mm. It really doesn’t make a big difference with these thicknesses in the space constraints we talk about. What we as contractors look at is the cost so as to get the same output on the same type or thickness of insulation. What it comes down to is the cost, the longevity of the insulation, the certifications involved, smoke values etc., and that’s how we take a decision. We as contractors put onus on construction, cost and durability.”
Hameed added later: “Apart from the design and the type of product, the main thing is the installation. Most of the time issues arise because of bad workmanship. As a principle, we should be having some kind of training for the people who are at the site, so that they know how proper installation can be done. That will solve at least 70% of the issues. Also, there should be regular visits done by the supplier. It should be one of the clauses that the consultants have given, but unfortunately they don’t do so. And even the suppliers don’t take the risk of going and inspecting.”
Nair defended the consultants by saying that it depends on who the consultant is. He said: “Some consultants look at 100% of the things, and there are others who don’t.”
Abdul Hameed, sales manager, Faisal Jassim Group.
At this point there were arguments as to which was more dangerous: leakage in a chiller water system pipe or ducts. Nair said that the temperature of the medium is different. “You are comparing 4-5 degree C of water being carried in pipes compared to 23-24 degrees of air,” Nair said.
Mishra argued that leakage in a duct will lead to some energy losses, whereas leakage in a pipe will lead to a disaster. Nair counter-argued that leakage in pipes is never an issue because you can see it and therefore it can be rectified. Nair said: “Leakage in duct is a bigger risk, because it is never seen.”
Clarifying his earlier stance, Mishra added: “A leaking pipe can actually destroy your false ceilings and other things. Leakages in a duct doesn’t cause any physical loss, but only mechanical loss or energy loss.”
Nair said that leakage is the biggest issue they face during commissioning. He said: “On every job, we spend a number of manpower and money to find ways to reduce leakages by way of commissioning, and during construction, this is not visible. In BK Gulf, we are putting a regime in place where we actually leak test all the ducts going into the concealed areas and shafts. It’s never leak proof but we limit the amount of leakages.”
Groves added: “I think you might be surprised with the savings. We’re doing a project now with a big multinational company, where the company’s insulation was not done properly. So we’re doing a complete analysis of with a consultant, for making recommendations. I think through proper ductwork and insulation, we can achieve meaningful savings.”
Anil Mishra, manager technical specifications, MEA, KIMMCO.
Regulations and responsibility
Groves believed that a lot of the consultants possibly may ignore these issues of ducting and insulation.
Nair added: “I would think the biggest problem is that none of the people who are involved in the construction phase are really responsible for the power later. The consultant actually designs; he’s is given some figures of how his design is optimised. When it comes to finally handing over, the bills are paid by the tenant. So the owner is not really bothered because somebody else is paying [the bill]. No tenant is not going to complain about paying 10 dirhams more. There is no onus on any of the designers to come back and say ‘I said that this building is going to cost so much’. Nobody does that. It’s all on paper, all the figures, percentages, etc. Unless you put the onus on the people who are selling or designing, to actually show that savings is achieved, it is pointless.”
Talking about whether guidelines are enforced, Mishra said: “In terms of leakages SMACNA, ASHRAE, etc., have worldwide standards that specify the type of sealing that you need to use for each duct to reduce the amount of leakages. What are the kind of connections that you have to do (herringbone or c-clip), whether transverse joints have to be connected and sealed, or longitudinal joints or any other connections where flanges should be connected to FCUs, AHUs or terminal points. These are very big standards and those standards are based on static pressure. Leakage is basically a function of static pressure. The more pressure you have in AHUs and the longer the duct is, the more are the chances of leakage. That has to be mitigated by implementing the standards. The onus first lies with the designers, the HVAC designers, to specify the kind of pressures that we have in the system. Be it is insulation, or sealants, there are relevant standards. It just needs to be enforced. As Sunil very rightly believes, from a contractor’s point of view, there has to be a balance between design and cost. If the contractor is implementing what is specified, and if the consultant is checking what implemented is as per the standard, I don’t see any reason why there should be a problem.”
Groves added by saying, “there is big difference between knowing how to and actually doing it”. Nair agreed with Groves that although there are regulations and standards with regards to installation, there is no regulation or onus on the consultants or the owners to actually prove that the right practice is happening. Nair said: “There should be a drive for everybody to save energy, and then some incentivisation, and finally, making someone responsible.”
Paul said: “The Dubai green building regulation is converting to Al Sa’fat (a green building rating system). And Al Sa’fat is trying to have a system of regular auditors of buildings.”
Mishra added: “It’s a good thing that institutes like Al Sa’fat are implementing the energy audit. The awareness has to be there. However, the whole work has to be from all angles, from the designers, fabricators, installers, contractors, etc. All of them have to be on the same plane, and then I believe over a period of time it will yield the desired results.
Hameed believes that the onus should be on all the parties, starting from the operator, consultants, contractors, etc. However, Nair felt that the responsibility should lie with one person. “If the consultant (or contractor) is taking money for the design, he/she should take the project all the way forward and be responsible all the way.
“A consultant is responsible for design, actual construction phase of it, inspections, handing over, testing and commissioning. All of those are a consultant’s responsibility. The parts are done by others, but he is responsible for inspecting. And that’s what the DM (Dubai Municipality) specifications stipulate. Everything that we submit to DM is through the consultant. It’s not a contractor’s submission. And a consultant is responsible to make sure there are no non-compliances”.
Paul Groves, Business development manager, Khansaheb Industries.
Best and worst practises
According to Groves, some of the best duct cleaning practices are the use of wire hanging systems (where appropriate); cleaning that requires limited access doors; modular units, which gives better installation quality, speed, uniformity, etc; proper testing; and proper acoustic design.
Some of the not so ideal practices are long lengths of flexible ductwork; no testing; poor acoustic design; no proper vapour barriers; full ductwork area not being insulated, as specified; internal insulation; and hidden damage to GI ductwork (under the insulation) not repaired.
Hameed shared his thoughts on design: “Basically, the design that they carry out in the GCC is the basic thumb rule. They are not catering to a project by selecting the design that the customer is looking for. What they do is by experience. This should not be the case.” He also reiterated his point that installation must be done properly.
He summarised: “Obviously the duct design has to be a prime thing; they should not be using lengthy ducts, sharp corners, etc. The second is the installation. They have to select the proper thickness, thereby avoiding unwanted use of energy. In short, ducting and insulation should be done in a proper way, thereby you are able to save energy and serve the purpose. Insulation is done for avoiding heat gain from the ambient [temperature] and thereby avoiding condensation.” Groves added one of the bad practices he has observed is the overuse of flexible ductwork. “Flexible ductwork has quite a lot of impact on airflow efficiency and I have seen some systems designed that are too long and changing direction several times. For flexible duct work to be changing directions, I just think it’s wrong.” Mishra added: “Fabrication is one issue which actually has a big impact on the functioning of ducting. Poor workmanship can lead to losses of up to 30%. Some of the flanges are not insulated properly. These are the factors that are not very ideal. Some contractors are good but not all of them. Not all of them monitor everything, and this includes consultants.”
With Expo 2020 coming up in the region, all participants agreed that there is a growing demand for ducting and insulation products. Moreover, in addition to accountability, proper installation and testing are key things to remember. The purpose of an HVAC system is to condition the air and not just move it around; ducting and insulation have a major part to play in it.