KIEAE Journal

Although studies on long-life housing have continued, long-life housing is not much popular in our country due to lack of the system PR and thus awareness, and low profitability as pointed in Kwon et al. (2014). To promote long-life housing, the government introduced long-life housing certification system in an effort to extend the service year of apartment housing in a long term and relieve public burdens on economic, social and environmental aspects.

Long-life housing inevitably involves cost increase by class of long-life housing certification while providing durability, variability, and ease of repair, which are equivalent to or above those of general apartment housing. Therefore, when housing planners supply long-life housing above a certain portion in a housing complex, they should consider cost effectiveness carefully while satisfying the mandatory requirements for long-life housing certification. That is, it is very important to know obtainable class of the certification and accompanying cost when applying the element technologies for long-life housing in the planning stage of long-life housing.

In this respect, the present study is aimed to propose element technologies influence matrix that can be used as basic data for making decision on element technologies to adopt in the planning stage of long-life housing. With this influence matrix, planner and business entity are expected to help make decision on technology or construction method in a fast and easy way because the matrix shows the changes in quantity, cost, certification class, and process by applied technology in the planning stage of long-life housing. Further, it is expected to contribute to developing tools related to long-life housing.

This study attempts to find various and technologies applicable to long-life housing by its key attribute; connect the characteristics of construction technicology, certification system that implements by the objective of policy, and required cost; and thus propose a method to evaluate the change in design elements when element technology is replaced.

To make “long-life housing influence matrix” that schematizes the impact that the attributes of long-life technology has on quantity, cost, certification class, and process, this study conducted the followings as below.

• ① Examining the characteristics of long-life housing: definition, core components, evaluation items of certification system, and performance class are studied.
• ② Reviewing the element technologies for long-life housing: element technologies applicable to long-life housing are listed by part.
• ③ Analysis of attributes by element technology: basic data (the characteristics of construction method in installation, dimensions in brief, evaluation items of certification related to applicable technology, obtainable performance class and score, cost per unit area) as well as connections (interface) that each element technology has are organized.
• ④ Drawing influence matrix: the matric is drawn in a way to include as many number of cases as possible to summarize the impacts of the changes in the element technologies upon technology itself and 4 areas (quantity, cost, certification class and process).
• ⑤ Verifying matrix applicability: the influence matrix prepared for unit household of long-life housing is verified for availability by applying it to calculate the changes in quantity, cost, certification, and process by applied technology and analyzing them.
• ⑥ Reviewing the possibility of developing a tool for automation: Tasks to which the matrix can be applied are reviewed and each function is reviewed for possibility of automation.

Long-life housing is defined as dwelling planned to cope with social change, technological change, household change, change in family composition and diversity by increasing the physical and functional lifespan of a house more than a general house (Ministry of Land, Infrastructure and Transport, 2014). Such long-life housing is a house based on long support of maintenance and with long-term durability and usability considering the change and replacement of infill (Kim and Park, 2014).

To make a house last long and maintain its functions and performance after long use, the structure itself should be durable enough and building components such as exterior and interior finishing materials and facilities should be designed and constructed to change and replaced in an easy manner to respond to changes (Jung and Lim, 2006).

Seeking one hundred-year service life, long-life housing is structured of highly durable column structure (support) and skin (cladding) designed to attach and detach PC or such, and the interior materials and house-specific facilities (in-fills) that should be designed to separate easily from the structure so they can shift and be re-installed (Lim and Lee, 2014). The structure support and infill for long-life housing equivalent to the skeleton and infill of Japanese SI housing can be defined as follows.

• ① Support: it is a structure, common facility and/or equipment that are decided for public interest. It has relatively long service life and is hard to change both physically and socially.
• ② Infill system: it is interior and/or house-specific facility that are decided for personal interest. It changes relatively more than a support physically and socially, having shorter service live. Especially, it is designed with lightweight nonbearing wall insead of existing bearing wall so that interior remodeling is easy to increase the life span of a house (Lee 2014). It requires high level of standardization and mass production (Hwang et al., 2014).

Long-life housing certification system is to certify the performances of a house such as durability, variability, and ease of repair, which is finally approved by the head of certificate authority. Here, durability means resistance to heat and variability means spatial performance of accepting various demands while maintaining the structural stability of a building. It is materialized with visually variable structures and spatially variable structures. Ease of repair is high and easy level of repair and/or remodeling of common and exclusive parts of a building. It also means high responsiveness to change.

Certification class of durability is evaluated and decided with concrete quality (thickness of iron bar covering, design criterion strength, slump, unit volume of binding material, water-binding material ratio, air content, chloride amount, and such) in case of ferroconcrete apartment housing. As seen in Table 1 that shows evaluation items of variability and ease of repair for specific area, the evaluation items are divided into ‘mandatory items’ and ‘optional items’. Variability is evaluated with 3 mandatory items and 6 optional items. Mandatory items include length ratio of bearing walls and columns, ratio of light-weight walls compared to all internal walls, and flexibility supporting methods. Ease of repair is evaluated separately for common area and specific area. Specific area is evaluated with 2 mandatory items and 4 optional items. Mandatory evaluation items for specific area include ‘providing independence for public plumbing and exclusive M&E space’ and ‘design easy for repair and replacement of plumbing and wiring’.

The element technologies for long-life housing mainly concentrate on in-fills. They are concerned with not only application of variability and ease of repair to in-fills at the stage of use, but also further analyzing construction methods between in-fills and between in-fills and supports.

As seen in Table 2, element technologies can be applied to various areas of long-life housing such as confining wall between housing units, partition wall between housing units, ceiling, floor, bathroom and others. The areas to which the element technologies can be applied are classified as below.

• ① Wall: lightweight composite, extruding (lightweight), functional gypsum composite board, autoclaved lightweight can be supplied by many manufacturers. It can be used for partitioning wall or confining wall between housing units.
• ② Ceiling: light-weight ceiling system can be considered to apply inside a living unit instead of general gypsum board ceiling.
• ③ Floor: it is possibile to apply floor heating panel (dry system) and access floor system in place of current wet Ondol heating floor system.
• ④ MEP: Considering independence, easy of repair, and flexibility in planning mechanical/electrical facility, wall plumbing method or slab down method can be applied to bathroom and showroom instead of existing floor plumbing method. Or non-plumbing a structure can be considered in mechanical/electrical work. It also involves planning of the size and location of facility space.

As mentioned in Chapter 3, the element technology influence matrix is developed on the basis of the characteristics of construction method, cost information, and connection to evaluation items. It shows numbers of cases of quantity, cost, process, and certification class of concerned technology, interface, and other areas, which change when applied technology changes or replaced.

Influence element matrix displays the impacts of change or replacement of applied technology. Since technological replacement takes place mainly locally (at a 'part'), the matrix is also prepared by area (part). Each cell in the matrix by area includes combined information of type and extent and level of impact. Level of influence is expressed in specific figures (numbers) or index. In the influence element matrix, the types of 'influence' are as below.

• ① Quantity(Q, Quantity) area: the element technologies for long-life housing are divided into many by area and construction type (e.g. wall, ceiling, floor, bathroom, facility and etc.). And for the same area, they are sub-divided by construction method and material to use. Change or replacement of applied technology brings direct change in the quantity of concerned item and indirect change in the quantity of interface item.

Fig. 1. 
Influences in Quantity according to Change of Technology

Figure 1 shows the case where the change of construction method for a specific area of housing unit has impact on the quantity of subsidiary material. As seen in the right bottom of Figure 1, decision on (or change to) light-weight wall type has effect on thickness and size of wall, size of ceiling and floor, and length of molding and base board.

These changes are included in Table 3 (Quantity-influencing Matrix). The impacts that the combinations of changes in 8 wall types inside a housing unit and 6 wall types between housing units have on quantity are categorized into 5 groups as below.

• • Change in wall area (a): in case interface type is different
• • Change in ceiling area (b): in case upper interface type is different. Or in case interface type is same but wall thickness is different
• • Change in floor area (c): in case lower interface type is different. Or in case interface type is same but wall thickness is different.
• • Changes in wall perimeter (d): in case wall thickness is different
• • Addition or deletion of element (e): in case upper interface type is difference and it is specified in a drawing

As seen in Table 4, actual change of quantity is expressed in numbers by the formulas combining wall length(l_w ), floor thickness(t_f), height of ceiling lower framework finish (h_c), and difference in wall thickness (t_w1 - t_w2).

• ② Cost (C, Cost) area: it shows the level of change in cost by combined effect of increased or decreased quantity when technology is replaced or changes and sum of unit cost. Unit cost for a, b, c, and d is applied respectively and increased or decreased volume of cost from original cost (when housing unit was designed first) is calculated.
• ③ Process (S, Schedule) area: change in technology has impact on work process and schedule of concerned item. In addition, it causes addition or deletion of other construction work, creation of new work, and/or change of process. For example, binding materials for upper/lower light-weight wall can change (differ) by construction method. In case upper/lower area should be fixed to the slab of a structure (S-S type) construction progresses in the order of “wall→floor→ ceiling”. However, when wall interfaces with ceiling and floor finish material (F-C type), construction should be carried out in this order: “floor→ceiling→wall”. When laying work of plumb pipes and electric wires in a structure is minimized, it reduces the required time for facility work in the current cycle of framework construction and thus changes the whole schedule of the facility construction.
  However, process change in the initial planning stage is less important than change in areas related to cost or certification. And detailed information of construction method or work process is often insufficient. Therefore, the scope of its influence was analyzed only briefly. When overall construction methods are determined and detailed process information is obtained, this matrix can provide a variety of information on changes in process and estimate the reduction of construction period as mentioned in Hong et al. (2009).
• ④ Certification (L, Long-life Housing Certification) area: the long-life technologies, mainly of in-fills, described in Table 2 are related to certification evaluation items for variability and ease of repair areas. replacement or change of technology in those areas have influence over certification class and score by item and eventually can affect housing unit and its certification. In other words, connecting long-life technologies to current certification system evaluation items of long-life housing, as seen in Figure 2, can confirm the changes in certification score and class by change in design elements. Because the certification class of a housing complex is interlinked with various incentives, which effects the profitability of the complex itself. Therefore, it is very important information to housing planning manager.

Fig. 2. 
Possible Influence Scope by Changing of Technologies

Internal Lightweight Walls: Inside Unit
Wall Symbols			W01					W03					W11					W21					W31					W33					W41					W51
Interface Types			Type I / S-S					Type I / S-S					Type I / S-S					Type I / S-S					Type II / S-C					Type III / F-C					Type I / S-S					Type I / S-S
Thickness(mm)			150					120					100					100					100					100					100					100
W01	S-S	150							-	-	-			-	-	-			-	-	-		+	-	-	-	-	+	-	-	-	-		-	-	-			-	-	-
W03	S-S	120		+	+	+								-	-	-			-	-	-		+	-	-	-	-	+	-	-	-	-		-	-	-			-	-	-
W11	S-S	100		+	+	+			+	+	+												+	-			-	+	-	-		-
W21	S-S	100		+	+	+			+	+	+												+	-			-	+	-	-		-
W31	S-C	100	-	+	+	+	+	-	+	+	+	+	-	+			+	-	+			+						+		-		-	-	+			+	-	+			+
W33	F-C	100	-	+	+	+	+	-	+	+	+	+	-	+	+		+	-	+	+		+	-		+		+						-	+	+		+	-	+	+		+
W41	S-S	100		+	+	+			+	+	+												+	-			-	+	-	-		-
W51	S-S	100		+	+	+			+	+	+												+	-			-	+	-	-		-
Internal Lightweight Walls: Between Units
Wall Symbols			W02					W12					W22					W32					W42					W52					* Classification of quantity influences a: Changes in wall area b: Changes in ceiling area c: Changes in floor area d: Changes in room perimeter e: Addition or deletion * ( + ) means "increase" ( - ) means "reduction"
Interface Types			Type I / S-S					Type I / S-S					Type I / S-S					Type II / S-C					Type I / S-S					Type I / S-S
Thickness(mm)			220					150					200					200					220					150
W02	S-S	220							-	-	-			-	-	-		+	-	-	-	-							-	-	-
W12	S-S	150		+	+	+								+	+	+		+	+	+	+	-		+	+	+
W22	S-S	200		+	+	+			-	-	-							+	-			-		+	+	+			-	-	-
W32	S-C	200	-	+	+	+	+	-	-	-	-	+	-	+			+						-	+	+	+	+	-	-	-	-	+
W42	S-S	220							-	-	-			-	-	-		+	-	-	-	-							-	-	-
W52	S-S	150		+	+	+								+	+	+		+	+	+	+	-		+	+	+

The influence matrix for long-life technology is expected to provide such information as below based on the attributes listed by key technology.

• ① A supporting tool for decision making in the planning stage of long-life housing: design elements in the planning stage, required cost, and a tool to explore optimum point among certification classes.
• ② Providing coast calculation for long-life housing cost: as the basic data that can be applied to a tool to change design elements of a specific area of housing unit or to create and re-calculate new details of change in construction method history when construction method changes.
• ③ Providing incentive data of certification system: When changes in certification system class and cost are connected to each other, it can be used as data for estimating cost required to attain target performance by certification class.
• ④ Providing inside-unit remodeling data at stage of use: long-life housing has significance in that it can bring various changes in response to resident's needs at the stage of maintenance and provide data for plane adjustment of a specific area and cost estimation s at the stage of use.

This study applied the influence matrix developed in Chapter 4 to decision making at the planning stage. Since this study focuses on the impacts that changes of technologies in a specific area of long-life housing have, it assumed that a housing unit is built in Rahmen structure with enough durability and applied with long-life technologies connected to variability. And it was also assumed that the reach of influence by change of technology is limited to concerned technology area itself and the interfaces.