By Ron Burns
Hotel developments are unique buildings and many times there are errors that creep into establishing the design requirements, since not enough attention is paid to what can go wrong.
We will look at two standard type “hotel developments” in this article, appreciating that there is the possibility that the designer goes for a more complex approach. Should this occasion arise then understanding the two simple options will provide the baseline for solving the more complex development.
Standard simple hotel building
‘Simple’ is defined similar to a typical South African Road Lodge development. Parking is external to the building and not under cover of a building structure. There will be no requirement for providing any smoke control to the parking.
The parking does get a little more complex when the parking becomes part of the structure with slabs over the parking. In South Africa we adopt the theory of a naturally ventilated parking, and I cannot support the concept of not providing any smoke ventilation to a parking facility, although this is generally accepted by the local authorities.
Please note that if the building does not contain sprinklers and is a multi-storey building, then smoke ventilation cannot be achieved. There are people who will adopt the principle of a “rational design”. I cannot understand this principle; it is not possible to control the temperature of the smoke without sprinklers and subsequently it is not possible to extract the smoke without losing the extraction fans on temperature. It is not possible to ventilate the lower level naturally; vertical venting is not an acceptable solution. Therefore if fans are required, smoke ventilation cannot be achieved without the use of sprinklers in the building.
Occupied floors and areas
There are a few important principles if the areas in the building share a common ceiling void. The building may or may not have meeting and/or function rooms. These need to be assessed in terms of 2 000m2 or 2 600m2 smoke zones based on whether the smoke ventilation system is natural or powered. A simple building will not contain any atriums and each floor will be separated from each other. The reception area may be double volume and this needs to be noted as high volume extraction areas, especially if there is a pedestrian bridge travelling over or access to the level directly above.
Although each room is separated from the common areas, this is not a reason to exclude evaluation of the common areas. Investigate the area of this space and the length of travel. Remember that smoke may not travel longer than 60m. I would caution the exclusion of smoke control from these spaces. There will either be a lift lobby and/or interconnecting stairs. These need to remain smoke free. Unless the lift doors are Class B, or equal, to an international standard and fitted with smoke seals, the lift should be treated as an internal chimney with potential for the fire to exit onto each floor. The chance of losing the building through the lift shaft becomes a concern that needs to be individually evaluated and addressed.
From a budgeting perspective, each smoke zone should be valued at the cost of a single smoke zone and added together. This is irrespective of the approach taken. There is no financial saving by using ducted shafts as opposed to a set of fans on each level per smoke zone. Generally a smoke zone comes at a fixed price irrespective of the engineering principle used. The 2019 budget rate for a powered system is R225 000 in South Africa. Please note this pertains to a simple building as described above.
Standard sophisticated hotel building
Standard sophisticated hotel buildings do not relate to the “Star Rating” system. They relate to the level of detailing and complex structure of the building. A simple building could easily carry a high “Star Rating” but from a fire perspective be simpler and easier to design.
Parking basement areas
As soon as the hotel has a basement, the building evolves into a sophisticated building. The basement requires a smoke ventilation system and a CO extraction system. The different lifestyles of the occupants need careful attention and no longer require a simple CO monitoring system.
Mean average weighting of CO levels become important. Normally a smoke clearance system is required, a basement automatically requires sprinkler protection, and if not for the protection of the structure, sprinklers are definitely required for the protection of the smoke ventilation equipment. The controls are complex, and evacuation of people is a primary concern that affects the control of the system.
Second, multi-level basements in the building move the building in to the complex space. The evacuation staircase adds additional complexity to the staircase pressurisation system. Air is required to be ducted to the lowest level of the basement. The stair cannot be pressurised from high level and pass the evacuation level and then extend below this level. It is not possible to get the air past the evacuation level without a ducted system.
Occupied floors and areas
The occupied level of the building requires similar attention to the standard simple building. There may be a scattering of double volume areas and this becomes an automatic concern, specifically from a financial perspective. A double volume area from a budgeting perspective equates to approximately three single level smoke zones (R675 000). Attention to the travel distances, less than 60m for smoke, need to be adhered to from a compartmentalisation perspective. Attention to the lift shafts remains paramount to the success of the smoke ventilation system.
Parking basement areas
Complex buildings consist of multi-level basements. The impact of the CO management which should be undertaken by the smoke ventilation specialist creates a high level of extraction with zero chance of diversification of the CO extraction rate. As an example, a three level basement requires double the extraction rate for CO versus the smoke extraction requirements. A 10 level basement (which is not uncommon in complex multi-level occupation buildings) requires six times the extraction rate for CO as opposed to the smoke ventilation requirement.
The challenges of the stair pressurisation system remain and are only marginally more complex due to the duct requirement. It is important not to let the air into the stair at too high a velocity or noise level as this is going to prevent the people from entering the staircase. Most people do not understand the dynamics of the pressurisation systems and will not enter due to fear created by excess noise levels.
Naturally the lift lobbies carry the same concerns as in the simple building. It’s a little more challenging in a multi-level basement as this creates a challenge with pressurisation and fire fighter access to a level below the fire to attack and extinguish the fire at its seat.A complex hotel is built to make a statement. The external façàde is one aspect, however the internal ambience of the space is where the designers take their licence to a special level. Multi-level atria are mainly the rule as opposed to the exception. Smoke channelling, is a requirement: open access and large spaces require astute planning when considering the smoke ventilation pathways.
When dealing with the atria it is important to prevent smoke bleeding into the atria, as this converts the atria into internal chimneys. The architect will have spent significant effort and resources ensuring the sight lines are not obstructed. This space needs to convey a specific feeling of uninhibited freedom, which cannot be achieved with glass, steel or concrete.
There will be a requirement for the installation of automatically operated fire curtains isolating the atria from the fire floors. The option of using the now enclosed atria as a smoke duct significantly reduces the requirement of multi–ducted smoke extraction systems, however there is a financial cost associated with the use of high level engineering.
Budgeting a project of this nature is a fluid exercise that requires the combination of various skills, as each option comes complete with its own unique set of challenges which, although conquerable, require astute application of code requirements. Caution rather than valour is paramount when approaching a hotel building which can, over the holiday periods, contain a high occupancy, who often are revelling in a party mode, paying little attention to escape routes. Ensuring their safety in the event of a fire is paramount.