Scottish Government

CHAPTER FIVE LIFECYCLE COSTS OF THE BASELINE DWELLINGS

Overview

5.1 Detailed lifecycle cost models were prepared for each of the baseline dwellings, based on the cost plans, drawings and specification information. For the flats, a lifecycle cost model was prepared for a 4 storey block of 8 flats comprising 2 x one bed flats, 3 x 2 bed flats and 3 x 3 bed flats. The elemental whole life costs were then apportioned for each flat on a m ² gross floor area basis.

Scope of lifecycle cost models

5.2 The lifecycle cost models comprise the following cost categories:

• Lifecycle maintenance and replacement works: major works typically occurring at a 5 yearly or greater cycle.
• Planned and reactive maintenance works: planned works such as boiler servicing, redecoration and voids maintenance, and unplanned works such as repairs and maintenance. A complete internal redecoration on a 6 year cycle has been included as part of the voids maintenance costs.
• Property management costs: costs incurred by social landlords in administering the above works. This category is also assumed to include insurance costs.
• Utility costs: costs of gas and electricity used in providing space and water heating and lighting, plus an allowance for tenant appliances.

5.3 The following costs are excluded from the lifecycle cost models:

• Tenants' rent charges
• Council Tax and water charges

Key assumptions

5.4 Key assumptions made in the development of the lifecycle cost plans and agreed with the project's steering group are outlined in table 5.1 overleaf.

Table 5.1: Key assumptions in lifecycle cost plans

Source of utility cost data

5.5 Gas and electricity unit prices are based on the Department for Business, Environment and Regulatory Reform ( DBERR) Quarterly Energy Prices January 2008 (tables 2.2.3 and 2.3.3) assuming an Edinburgh location and credit payment of bills. Gas and electricity consumption rates for regulated uses (i.e. heating, hot water, lighting) are based on the benchmark data within the SAP-based calculation software. A general allowance has been included for tenant's electrical appliances. Gas or electricity for tenants' cooking appliances has been excluded from this study.

5.6 The assumed gas and electricity consumption figures used in the lifecycle cost models are summarised in table 5.2 overleaf.

Table 5.2: Assumed fuel consumption data

Maintenance and component replacement assumptions

5.7 Maintenance frequencies and building component replacement cycles are based on a combination of published data sources, Building Research Establishment ( BRE) research, BCIS data and our experience in the social housing sector. Key replacement intervals are as follows:

• Kitchens: 20 years
• Bathrooms: 25 years
• Internal redecoration: 6 years based on assumed void cycle
• External redecoration: 5 years
• Boilers: 15 years
• Extract fans: 7 years
• Rewire: 30 years
• External doors and windows: 25 years.

Summary of lifecycle costs

5.8 The estimated lifecycle costs for each baseline dwelling are summarised in table 5.3 in current costs and discounted to NPV using a 3.5% discount rate. The current cost totals exclude capital costs. The NPV totals include capital costs.

Table 5.3: Lifecycle cost summary for baseline dwellings

Elemental breakdowns for each dwelling type are included in Appendix B.

Use of capital and lifecycle cost models in assessing EcoHomes and CO ₂ improvement options

5.9 The completed capital and lifecycle cost models for the baseline dwellings have been used to assess the cost implications of a range of potential options for improving the EcoHomes and CO ₂ performance of the dwellings. The output from this exercise is presented in chapters 6 and 7.